It's a lot more fun to be using that pretty piece than leaving it in a box in the closet -- I find I am emotionally rewarded by FINISHING something, and I can't finish it if I don't start it! Yes, using a little bit of a larger piece MAY leave you short in the future, but that's a quilter's life -- I once needed 2"more for a quilt back that I didn't have because I had cut a 6" square out of the corner of a large piece! (I had to go buy 6 1/2 yards new for the back.
)