Maybe your illusions about Santa crashed a long time ago. Never mind! There are still plenty of reasons—five, to be exact—to go through life expecting the very best.

We'd just finished decorating the Christmas tree. Covered with pine sap and puncture wounds, I was snarfing down a soothing pound of chocolate when my 6-year-old daughter Katie asked, "Mommy, what's that?" She pointed to a single pine needle that, curiously, appeared to be levitating in midair about four feet away from our new tree. Squinting, I saw a tiny string of spider silk connecting the needle to the ceiling. I thought of brushing it away but decided I was way too tired to walk across the living room. "Oh," I said, "why, that's the…the Magic Pine Needle! Don't touch it! The reindeer need it for…uh…morale."

Fast-forward a year. Now Katie was 7, and along with her younger brother and sister, she'd just helped me put the finishing touches on a blue spruce. "Okay!" she crowed when the last bauble was hung. "Now all we need is the Magic Pine Needle!"

"The what? Oh, right! The Magic Pine Needle!" I rubbed my eye, which felt like it had been stabbed by a stray branch. "Um, well, see, that was a one-time deal. Every family gets the Magic Pine Needle only once in a lifetime." All three of my children stared at me as though I'd just stuffed Santa into the trash compactor, along with the miraculous Hanukkah lamp, the Kwanzaa candles, and the baby Jesus.

That was the only time in my life I have actually gone looking for a spider. I never found one. Ever since, the memory has reared its accusatory head whenever my children show the slightest sign of dysfunction. Teenage cynicism? Computer-game addiction? Disinterest toward math? Part of me believes that if I'd just kept my mouth shut, avoided creating unrealistic expectations, I could have averted them all.

But of course, the real issue isn't the Magic Pine Needle. The real issue is managing assumptions. Many of us have misconceptions about how to do that, but expectation management, so necessary this time of year, is a vital skill you need no matter what the season.