Finally, a kindred spirit! When I try to "square up", I wind up whittling the quilt smaller and smaller. Same thing happens on blocks. So I really concentrate on cutting the fabric accurately and sewing consistent seams.
Somehow, without worrying about squaring everything up, my quilts come out mostly square. So far, no one has complained about the quilt they get being out of square.
I stopped feeling bad about my slightly off-kilter quilts when I started quilting charity quilts by others. The backing for the first one I did was cut so short and kind of curved, that I couldn't use it. The quilt top and back were done by a very experienced, respected quilter, and I was hesitant to speak to her about it. Such a dilemma!
Finally,I just called the her and told her about it. She basically said, "Find a way to make it work! You won't hurt my feelings." So I did. I used a different fabric for the backing and then used the backing to make a pinwheel quilt.