The first thing(s) I learned about quilting. THREE things can make your block(s) come out correctly or incorrectly.
1) cutting
2) sewing
3) pressing
There have been times over my years of piecing that one, two or all three have affected my blocks.
I have added some more, that I have learned from experience;
4) mood affects my production
5) slow down, being fast is not always accurate.
6) relax