The way I feel today, as long as my health is good and I can handle myself well and people still come to my concerts, still buy my CDs, I'll keep playing until I feel like I can't.
At some point, you can't lift this boulder with just your own strength. And if you find that you need to move bigger and bigger boulders up hills, you will need more and more help.
I became intrigued with colour theory. The absurd pronouncements of the Colour Institute, a group that decides what colours are hot each year or season, amused me.