I struggle with this, too! I just started making a pretty straightforward lap quilt for my son - something he requested - and I went into my bin(s) of leftovers to look for appropriate fabrics. I found a perfect gold-on-gold and a perfect red-on-red, and enough of both. But it took every bit of willpower I had to actually use them!
I'm sure I purchased both at least four years ago, and I marveled at 1) how much I still like them and 2) how much better their quality is than much of what JAF has to offer these days. My instinct was to save them. I had to have a stern talk with myself that went along the lines of: "Save them for what? A quilt for your son isn't good enough? Do you have another plan for them? If you never use them, just what do you think will happen to this fabric when you die?"
I forced myself to use them. Sure hope the quilt turns out well!