I had to learn to Press not Iron. I ruined several quilt squares this way. Even if you cut perfectly(NOT ME) sew perfectly(STILL NOT ME) you can stretch or mess up your shape when you iron. Lesson learned. I didn't use to press or iron at all but it made a difference in a warm wishes quilt i tested it on. Then i ruined my first diamond star block. Hopefully I will do better. I learn so much here with so many great people teaching!!!