When you’re a child, the hierarchy of Jewish holidays is clear and unequivocal. Purim, day of pandemonium, reigns supreme, with its costumes and its cookies and its invitations for mischief, followed closely by Hanukkah and its eight crazy nights and Passover, purveyor of the afikoman and its bounties. Sukkot and its festive decorations, Rosh Hashanah and its honeyed apples, Yom Kippur and its comforting quiet all follow suit, delightfully obvious even to an 8-year-old. All, that is, except for Shavuot.What, after all, has the holiday to offer to the young and the restless? Blintzes are nice, but look at Shavuot through the bright eyes of a child, and you’ll see little to amuse or delight. Until, that is, you wake up one morning in Sivan and discover that you’re in your forties and Shavuot is your favorite new holiday.Just think of the holiday’s many and subtle meanings. For one thing, it is, as former Senator Joe Lieberman reminded us in a lovely little book this year, the holiday of laws: Having fled from Egypt amidst a throng of divine miracles, the Israelites, still giddy from all that Godly love, must now receive the Torah and settle down to the decidedly grown-up business of obeying its edicts. They must, in other words, replace careless ecstasy with contemplative obedience, which is about as sharp a metaphor for adult life as you’ll ever find.Do that, and you’ll discover another humbling truth: We are all, in the most profound sense of the word, converts. None of us were born blessed with an innate knowledge of truth and beauty; they are offered to us, as the Torah was to the Israelites in Sinai, and we must choose to accept it out of love. If we do, we’ll thrive, not despite all of its hardships but precisely because of them. That is why we read the book of Ruth, the first Jew by Choice, on Shavuot: We are all Ruth, every day anew confirming our faith and our peoplehood.Which, really, are ideas that only begin to resonate when you enter the fifth decade of life. These days, most of us spend our twenties and thirties extracting life’s pleasures and promises, working hard on building careers and families while taking in as much as we can of the world’s bounties. But it’s not before we hit 40, I think, that we begin to understand just how fragile our collective fabric truly is, and just how essential it is to protect and preserve it. At 40, we begin to understand that the traditions and the laws we’ve always jabbed with youthful joy, finding them antiquated and needlessly stifling, are there for a reason. We begin to understand that even if we choose to reject substantial portions of our heritage, it is still there in our hearts, asking tough questions and demanding answers. When that happens, there’s nothing that gives us more pleasure than to spend a holiday eating cheesecake and arguing over text, with none of the wild euphoria we had once felt as children but with a new, quieter joy we wouldn’t trade for all the Purims in the world.