Not specific to comics, but a solid gold guide to making creative work. This stuff has been invaluable me making the transition from corporate drone to livin'-the-dream creative guru :-) I've listed some of my favourites below, but I highly recommend taking the time to read them all (also these are just the titles, each one also comes with a little kick-up-the-ass essay). Then print them out and put them above your workspace. Or your bed. Or both.
1. Ignore everybody.
3. Put the hours in.
13. Never compare your inside with somebody else’s outside.
14. Dying young is overrated.
15. The most important thing a creative person can learn professionally is where to draw the red line that separates what you are willing to do, and what you are not.
21. Selling out is harder than it looks.
24. Don't worry about finding inspiration. It comes eventually.
30. The hardest part of being creative is getting used to it.