To me squaring up as I go is one of the most important parts of making any quilt. Second only to pressing each seam as I go. I for on am challenged on making exact and straight seams so I need to press and square up each section of every block to make the perfect block I then again check the blocks to be sure each one is square before sewing them together. At the last seams I then square up the sides again to insure things are correct. I can still come off a bit and be out of square but then square things up at the end with a bit of stretching here and there..