A piece of sound advice from Anna:
Every difficulty slurred over will be a ghost to disturb your repose later on.
-Frederic Chopin

I find this particularly meaningful. This quote is generally about practice - if you leave the difficult parts out and not work on them, these parts would affect the structure and quality of your piece. But if you work on the little bits, yet look at your piece(s) in a bigger perspective, you tend to improve the quality of your piece heaps more.

It's really cool that I can get sound advice from an amazing piano teacher (who's a concert pianist too) and an absolutely wonderful tutor (who's a professional cellist).