Agree - was working on a quilt the last few days that is made up of 20 16 patch blocks set on point, with hourglass blocks in between. Cut 20 sets of hourglass blocks, and then proceeded to sew them into 20 blocks, press and trim.
Went to sew the two sets of block together, and realized that a bit under half of the hourglass blocks needed to be ripped as half blocks are used for the setting triangles all around the outside of the quilt. Had I stopped and looked at the pattern before starting on sewing the hourglass blocks, I'd have realized my thinking was not correct.
But that is why I keep a seam ripper at my sewing machine, and another at the ironing board - ripping is just another part of the process for me,