Math vs Memoir

Summer has finally come to Switzerland. So why do I wish I were working on a math problem instead of a memoir?

Because once I found the solution to the math problem I would be done. Finished.

How boring.

How wonderful.

Instead, I’ve got to decide for myself when each piece and part of my book is done.

This is hard. I'm used to hard. I live in a country where people speak in one language and write in another. But still.

When you're writing something, how do you decide when it's finished?