Racquetball.

I took it as one of my FRA (fitness and recreation) credits in college, and then started playing regularly with a bunch of friends. No one in the class, or any of my friends ever beat me. Every now and then it was close, but not very often.

Then my brother in law started coming to play with me, and I realized that I was nowhere near as good as I thought. He absolutely wiped the floor with me. He played squash most of his life (he's british), plus he's super athletic, and he literally just had me running all over the place trying to stay alive, much less do anything to actually try to win.

Then I watched the pros on youtube, and I can't even tell there's a ball in the court. It's freaking insane!

Still love playing, but now I know where I actually rank in the grand scheme of things.