Oh, boy... I think it really could easily become a real addiction for me! I do try hard to be a good steward of my resources, though, and not let myself get too carried away.
What I tend to do is get inspired by fabric I see, think of a quilt that I'd want to make out of it, and buy it to make that quilt. Honestly, over the past 15 years, I've only really bought fabric to make about a half a dozen things (I've really been an off and on quilter for a long time, plus I hand-quilt so I'm slow) so it's not like I'm spending tons of money on fabric all the time. I do have a considerable stash, but mostly because I keep inheriting fabric from my quilting grandmother who weeds out from time to time. And there's always extra fabric left over from every project, especially if it's one I abandon partway through. : / I am happy to say, though, that I've just completed a full-size top made entirely from scraps from my stash, so I am using stuff I have, not just accumulating! I guess that's my plan- buy for specific projects I have in mind, then make a dent in the stash with a scrappy from time to time!