I usually check my blocks before I sew them into rows and yes, I do square them up if they don't match. Then I press each row so the seams nest when the rows are assembled. That way it becomes clear immediately if something is off. IF it is off, I gauge if the problem will be noticeable when the quilt is done OR if it bothers me. Then I take out (cursing of course) my booboo and fix it. I may lose some time, but the result will make me much happier.