Some days you wake up and well, kind of like in the spirit of Keith Richards, you think, "I'm just happy I did wake up." Then there are those days you get up and well, you're happy to be on the planet, to be walking around and basking in the pure pleasure of existing. Then there are those days when that's not enough, you actually want to make your mark, to leave a legacy, or a body of work, or be remembered for something. I guess it's a matter of ego, or ambition, or a way of imagining a certain kind of life after death.
You'd think maybe the Zen way would be enough, live lightly and leave no trail. But then you can't help rearranging the rocks, or leaving a footprint, or bending a branch, just to leave some proof that you once walked these paths.
Some days you have to write the next play, record the next song, not because the world is clamoring for the work, but because you can't imagine not doing it. Whether what you create has any life beyond the moment is not a question that needs to be answered. It doesn't even need to be asked.