Today, I had a piano lesson.
I learned that typically, you can not play a sharp or a flat, using your thumb. Thus, playing the piano with proper fingering is helpful.
Not only that, if you learn to play something incorrectly, it's always a bit more tricky to unlearn it...and relearn it.
So, your hands have to look as pretty as the music you are playing. Not sure who made up that rule. But it's something to strive in your piano playing endeavors.
What did YOU learn today?