I just love fabric!
When I buy, I may or may not have a particular project in mind. For me the fabric tends to dictate the design I will use. Sometimes a piece of fabric will 'speak up' and demand a particular means of showcasing it's beauty...just gotta listen!
Also I usually have several in the 'thinking stage'...want to do a quilt in say black & white, don't have a clue what design I'll go with, but know I want to have quite a few different black and white fabrics - black on white, white on black, small print, bigger print, maybe a polka dot or stripe, and so on...
I've never yet bought a pattern, just found pictures of something I liked and taken it from there. If I did buy a pattern I'd most likely change it up somehow anyway!