I understand this tendency, but I've gotten over it (mostly) by telling myself that there's no point my spending the time making something out of fabric I find ugly. I can make only a limited number of quilts in my life, so shouldn't I be making them out of fabrics that I love? If I'm making something for myself, the question is: Don't I want a quilt/bag/skirt made out of something I love that I will then see regularly?
The other coping mechanism I use is to buy a lot of something I really love. Then I can use it for something and tell myself that I'll still have some left if I want to make something else out of it. I sometimes do, but other times I feel like I'm done with it.