Cutting and sewing to get a precise size does take skill and you have to develop that skill. I am a believer in quilt classes from knowledgeable instructors. I don't mind showing my not right blocks and asking what do you think I did wrong. I watch others cut and sew and that helped me a lot. If you can't go to a class use Craftsy. I learned about thread types, weights, and ply. I learned about needles. That made a difference in my stitches. If I stop sewing for an length of time I forget little details that make or break a good sew. Takes me a mistake or two to remember!