I first heard the expression in an article about resolving writer's block [1]. While that particular article is specific to role-playing games, the idea has more general application and I've heard other writers refer to it.
The basic idea is that you can't always be creating. You're never as original as you think you are; your output depends on your input. If you are a storywriter, you need to remember to read for pleasure. Seek new experiences, consume the things that are innovative or interesting or just plain cool in your field of choice. If you keep your muse well-fed on interesting ideas, she'll be ready to provide you with new ideas when you need them.
It applies even in a technical context. Even if you are forced to work in Java or Ada or on a horrific enterprise application, you should be playing in Haskell during your free time, reading papers on interesting algorithms, doing recreational mathematics, that sort of thing. The ideas that will come to you when facing your work are much improved by play.
My own creativity-killing bad habit is to starve my muse. Either to drown myself so completely in the act of creation that I run out of ideas, or to intellectually consume crap rather than good stuff.
> 5. Starving your muse
Care to elaborate? Looks like something worth thinking about.