Last fall, I wrote a blunt email to Nick, male friend. I wasn’t exactly “unfriending” him, to use social-media-speak, but I was pulling away.We hadn’t had a fight, and he hadn’t done anything wrong. But I’d met Nick when I was single, and now that I was five years into my marriage, I’d realized that our friendship had become imprudent.I’d judged my Orthodox sister harshly when she had made a similar move, cutting off friendships with men after she got married. As a Conservative Jew, and a rabbi, I didn’t have the same notions of tzniut, modesty, that she did. And yet, for different reasons, I’d arrived at the same conclusion: I had to dial back my friendships with men for the sake of my marriage.My sister and I are identical twins, but our physical resemblance is contrasted with our clashing garb. I’m the pants-wearing, bare-armed, hair-showing one; my sister is the one dressed collarbone-to-ankle, covering her elbows and hair. These different uniforms suggest the larger differences: I’m a tefillin-wearing, Torah-chanting, service-leading Conservative rabbi, while my sister (who is also my best friend) sits happily on the other side of the mechitzah from the rabbi in her shul.Growing up in a traditional—if not fully observant—Conservative home, we diverged religiously over the years, but those gradual changes became more precipitous when she married an Orthodox man when I was in rabbinical school. While I studied Talmud and engaged with feminist liturgies, my sister let her husband do the Gemara-learning and minyan-making for both of them. Among the changes in her life that startled me most was when she dropped a few of her closest friendships—specifically those with men.I was appalled. The modest clothes were one thing, but when she no longer maintained what were once dear friendships, I felt like her friends were becoming collateral damage in my sister’s striving for tzniut. I hated that my sister was now living in a community in which people’s gender prescribed (and proscribed) the communal roles and social spheres accessible to them. I didn’t like that my sister’s marriage seemed to limit her availability to her past friends and worried that it was the beginning of her disappearance into what I perceived as a narrower world. I didn’t exactly fit into her world, either; was she going to abandon me?Meanwhile, I continued to nurture friendships with both men and women. Although I certainly had relationships with men that were fraught with sexual tension, others were harmonious, sort of brotherly. Moreover, I found myself unable to turn any of my friendships with men into more romantic relationships, even when I wanted them to go that way. I felt a sense of pride that I could have deep friendships with men—even ones I found attractive—and be “mature” enough to put any sexual stirrings aside and relate to them as human beings.My friend Nick and I met during the first day of orientation when I returned to school in Berkeley at the Graduate Theological Seminary for a Ph.D. Both members of clergy (albeit of different religions—he is Catholic), we had similar senses of humor, worldviews, professional interests, and work habits, encouraging us to partner on a class project and sign up for some of the same classes. We both were deeply interested in how people live out their values and beliefs in the complexities of the contemporary culture. We passed notes in departmental meetings and hung out outside of class. Nick and I could never date—his religious order requires chastity, and a relationship between people dedicated so deeply to two such different religious paths would be way too impractical and unfulfilling to even consider. But we enjoyed each other’s presences and sought each other’s ears when we needed to talk things through with someone gentle, soulful, and understanding.Very shortly after I met Nick, I met Joshua—the only man with whom I was able to start as a friend and successfully transition into something more. Joshua frequently socialized with Nick and me, and he displayed no jealousy or lack of trust about our relationship. When Joshua and I got married, Nick helped me move into our new home and spoke at our wedding, but he and Joshua never developed a separate friendship apart from me. I moved across the bay to the peninsula, dropped out of school, dealt with some health issues, got caught up in new teaching jobs and newlywed life. Occasionally, Nick and I would visit, usually going out with other friends or celebrating occasions with families. By the time he finished his Ph.D. and moved away for work, we already had drifted away from each other somewhat. But we still corresponded as close friends over email, writing meaningfully of the adventures and challenges we each encountered.My husband is a mensch, a dedicated friend, and a terrific dad; I feel like we can resolve any crisis together. The best teams are composed of people with different skills, perspectives, and journeys to the field. And Joshua and I are definitely different.In the traditional Jewish marriage blessings, the bride and groom are called “beloved friends” (rei’im ahuvim). This ideal vision of marriage is a radical departure from the marriages of economic necessity, political alliance, and parental preference (if not demand) often evoked by stories of traditional cultures. Yet, my friendship with my husband is not the easiest friendship I have ever had. Joshua does not just instinctively understand me. We find each other both utterly banal and utterly mysterious. We have to constantly explain ourselves, and our misperceptions of one another’s motivations and preferences often trip us up. The spiritual lens through which I interpret life is foreign to the way Joshua looks at the world, and I can’t even begin to enumerate the ways in which Joshua’s inner world is unfathomable to me.Judaism doesn’t see this as a problem. In Joshua’s techie language, it’s “a feature, not a bug” in marriage. The Torah describes the original human (Adam) as requiring a “helper counter to him” (ezer kenegdo), which the ancient rabbis understood to be a partner who complements and supplements. In other words, opposites not only attract but also help us. Striving to reach a beloved who is so different from me is a holy action—involving communication, cooperation, negotiation, and patience—which builds me into a more complete, more fully realized person.Last year, after we’d been together for seven years, Joshua found me crying myself to sleep one night. He asked me whether he could help. At first I said no. Then I spilled my guts. I realized that Joshua is probably not going to be the person in the world who understands me most easily. He can love me best. He can be my biggest advocate. My most intimate lover. President of my fan club. But he just doesn’t automatically “get” me the way a few others do. Like my sister. Or Nick.And there’s the rub. A new work position had brought Nick to Los Angeles, where family frequently brings me. I was really excited at first, thinking I’d get to see him whenever I was in town. In practicality, the challenges of scheduling a visit with him alongside an overwhelming number of family obligations made it difficult. Then, it happened: I thought I had some time to meet Nick one evening, and I found myself not wanting Joshua to come along. At first, I wasn’t sure where the feeling was coming from. Then I realized that I was longing to pour out my heart to someone, and Nick seemed like both an ideal candidate and—because my husband should have been my primary confidant—the wrong choice. I decided not to see him, and that’s when I wrote him the email. Nick responded with his usual generosity of spirit, recognizing that modesty is an important value and has a particular valence in Judaism. We still write occasionally, exchange notes and photos on Facebook. I don’t feel like our contact is superficial. But I can’t go back to the type of friendship we had where we sit down and pour out our hearts in person. I don’t think that Nick resents me or my choice. He is sincere and wise. Once again, he understands me.Maybe the reason I can’t invite that level of familiar friendship with men (other than Joshua) anymore is simply that I am not a casual friend; I am devoted to and deeply involved with my closest friends. Maybe it’s because I am a twin, a person whose first friendship precedes birth. Maybe it’s because I take to heart the words of our tradition: “Acquire for yourself a friend” (Pirkei Avot 1:6). And how do you acquire a friend? The rabbis’ elaboration of Pirkei Avot (Avot deRabbi Natan) says, “A person should acquire a friend by eating and drinking with them, by studying Torah and debating with them, by lodging with them and by sharing private thoughts with them.” It’s still a useful formula for creating friendship. Particularly that last part.Truth be told, I’m a little more discreet in my friendships with women, too, since I got married. I don’t unburden myself to my female friends either as often or in as detailed a way as I did in the past. Yet I feel a special danger when the friend is a man—there’s something intimate about spilling one’s guts to a friend. That’s what is potentially immodest about a friendship between this married woman and any man other than my husband. Confession can be sexy, and dangerous.A friendship with Nick—or any other man with whom I have that automatic affinity—is a little perilous. That instinctive familiarity isn’t developed by an investment of time and effort; it isn’t earned by action or respect. It’s illusory and untrustworthy. I’m not even entirely sure where it comes from—similarity of disposition, or chemistry, or magic. Whatever its mysterious origins, that automatic affinity gives one a powerful feeling of being deeply seen and understood. It is as if that other person sees the secret you. Now I want only Joshua to know the secret me.How was my email to Nick different from what my sister did with her friends? My sister believed that any close friendship with a man was inappropriate and potentially immoral. I think she felt justified, perhaps even rightly so, in cutting them off. I, on the other hand, felt apologetic. I experienced a deep need to be open about my discomfort, to reassure my friend that he was still very dear to me even if I had to pull away from him—not entirely, but in a way that felt unnatural to our previously open and honest friendship. There was never anything truly inappropriate about my friendship with Nick. On the contrary, our friendship was probably helped by the fact that we were—for all intents and purposes— romantically off-limits to one another.Most of all, it’s not because of Nick’s exceptional familiarity with me that I needed to curtail our friendship. It’s really because of me and the energy and intimacy I need to direct toward Joshua and nurturing my friendship with him. Part of the power of monogamous sexuality is that it creates shared secrets, but it needs to be paired with greater self-revelation to be truly meaningful. And real self-revelation is something that takes time and effort. Instead of expecting Joshua to read my mind, I have to frequently unburden myself to him verbally; instead of allowing my unmet needs to fester, I have to open myself to him and expose my vulnerable bits, knowing that—unlike others—he’s earned that privileged knowledge.