I was a founder and play piano. The huge difference between these is that playing the piano is perfecting the task of playing the right keys at the right time in the right way. It's difficult because you have to train your body to make quick and precise movements, but you at least know what you need to do.
My experience as a founder (no outside funding) is that every day has a surprising new challenge or three, so it's more like managing chaos rather than doing drills. Or, compare it to juggling, but instead of getting to master juggling 3 balls before moving to 4, you have a bunch of people throwing balls at you and you have to keep juggling as many as you can and pick the ones up off the floor when you get a chance.
My experience as a founder (no outside funding) is that every day has a surprising new challenge or three, so it's more like managing chaos rather than doing drills. Or, compare it to juggling, but instead of getting to master juggling 3 balls before moving to 4, you have a bunch of people throwing balls at you and you have to keep juggling as many as you can and pick the ones up off the floor when you get a chance.