Comfortable with the struggle
Bookmarked Comfortable with the struggle by Rach Smith.
If I had to pick one trait, it would be the ability to be comfortable with “the struggle”. That part of the day/hour/minute where the code isn’t doing what you expected, things aren’t looking like they should, or where things are going wrong and you don’t know why.
Rach presents this advice in the context of cultivating a career in web development. I think it is just as relevant in a broader context. Doing anything at all well is about being comfortable with the struggles it entails. It goes for web development and any other career path, writing, exercise, playing an instrument and so forth, and so on.
If you can identify pursuits where you can learn to be comfortable with the struggle, professionally and otherwise, you're setting yourself up for a good life.