A while back I read an interview with the mathematician Conway where he said something that I regularly think of.

To be a great mathematician, you have to be comfortable with something not being finished, not knowing when it'll be finished or whether it'll ever be finished (by you). You might work on a proof for years, not knowing whether you'll actually solve it.

Whenever I have anxiety around some unfinished project at work, I think of this quote. I'm not a mathematician, but we can all learn to accept ambiguity and incompleteness.

I'm fact, the mathematician Gödel, showed that every conceivable mathematical framework is incomplete, because it contains unprovable statements.