Sounds like you are beating yourself up over the idea of perfection. Perfection comes over years of practice and patience then remember fabric moves, it stretches or shrinks depending on how you press it. If you want the "perfect block" mark on your ironing board with a ruler the size then pin your block to the marks and press it to fit. I have been a prolific quilter and enjoyed the process take a class like you thought about. You have been given a lot of really great advice here, now enjoy your learning process. But breath and don't be so hard on yourself.