It happened out of the blue, as such experiences often do.

I had parked my car and was walking a short distance from the public parking deck on a covered concrete sidewalk, past the open expanse of lawn and twinkling Christmas lights in front of the hospital. I was going to visit a friend who had just had surgery, and it had been quite some time since I had been in this hospital for any reason, personal or professional. As I walked, I happened to glance off to my left, and it hit me.

This is where we used to take my oldest daughter (who is now twenty-nine years old and has kids of her own) to daycare when I was in residency and my wife was working as a pediatric nurse.

It was a very brief, very concrete thought, attached to nothing, triggered by nothing more than the sight of a brick building. I was struck by how visceral this memory was, how it instantly transported me back to a simpler time when I was in school, had been married but a few years, and had one child.

I’ve had memories and thoughts like this hit me before, and I’m sure you have too. It seems that at holiday time, these kinds of memories bubble up to the surface more often than at other times of the year. Why, you might ask?

Memories that are associated with our senses are some of the strongest, most tenacious memories we make. Think about how one whiff of Christmas cookies takes you back to your grandmother’s kitchen in a way that feels so vivid you can almost feel the hot stovetop. If you close your eyes, you can taste the icing that you licked off your fingers after they swept the glass bowl once, twice, three times around to catch all the sweetness left there. Think about the perfume your mother wore on Christmas day when you went to church as a family. Anyone can wear that perfume, but only your mother smelled the way she did when she wore it. Smell the evergreen goodness of a freshly-cut and fresh-bought Christmas tree and you are back in your living room, a kid on a mission to shake, rattle and roll every wrapped present until you either knew what was in it or got caught and told to stop.

Taste cranberries and you remember your aunt’s favorite way to make them. The first bite of turkey this year will remind you of the first Christmas you came home after starting college. How good that bird tasted, because it wasn’t about the turkey. It was about coming home.

Touch the tinkling glass ornaments, hear them make that little musical sound, and you instantly remember the story of how they came to hang on your tree. See the lights on the tree and remember the year that all of them were strung before you realized that one string was completely dead and had to be replaced.

Sensory memories are the absolute best. You can think all you want about the holidays and what they mean to you and your loved ones, but nothing can replace the feeling you get when you hear, see, taste, smell or touch something that instantly brings joy to your heart and a tear to your eye.

Merry Christmas.

And thanks for the memories.

Greg Smith is a psychiatrist who blogs at gregsmithmd.