I blame my back for my UFOs. I can only sit for a short spell at a time. This is ideal in the sewing room -- pin a little, sew a little, press a little -- up/down, up/down, etc. To make any progress on quilting, one must sit and sit and sit. So that's why I progress more slowly with quilting than with piecing. If I need a standing break, I can always start cutting a new quilt!