For me, the primary purpose of documentation is to help myself in the future.

I don't view it as something I'm writing for someone else anymore.

Ultimately, I think that's helped me write better documentation.

Writing for an imaginary audience is typically harder than writing for a concrete one, and things you might think "someone else" might need to know - they either 1) don't, or if they do 2) won't read your docs anyway, most of the time.