That I will never enjoy the taste of wine.
I figured out I would never like coffee in my teens, and had the same realization about beer in my 20s.
But it wasn't until this year, in my mid-thirties, that I finally accepted that I don't like the taste of wine and probably never will. After years of trying the full spectrum of wines, I had to admit that it wasn't the "notes" that were turning me off, nor was it a problem with the quality of the wine. It was the fundamental "wine-ness" that I disliked, the same as I don't like the "beer-ness" of beer or the "coffee-ness" of coffee.