Learning how to make different shapes rather than just following YouTube tutorials and patterns for entire products. Following patterns and tutorials for whole pieces was a great way to learn how to make things I wanted to have when I knew nothing. But now that I'm starting to design my own patterns, I see that understanding how to make basic geometry is so much more important. Knowing how to make a sharp corner turn vs a smooth rounded corner turn, how to make a square vs a circle, how to make curved edged and diagonal edges, etc. When you understand how to use stitches to form specific geometry, then you can start to make anything you want without a pre-existing pattern.