I went and bought myself christmas presents and ended up spending a lot of money on books. I picked up a small one called 'It's not how good you are, It's how good you want to be.' It's just filled with little ancedotes and points about being a designer, but it can apply to many art-things, I think. I feel like sharing my favourite quotes becuase they seem relevant.

Do not put your cleverness in front of the communication.
If you get stuck, draw with a different pen.
Do not covet your ideas. Give away everything you know, and more will come back to you. (my favourite)