Cutting too many strips for binding- even though I always do the math to figure out how many I need. Forgetting to write down what batting(s) I used when quilting a quilt that I intend to show is another mistake that I make a lot. You’d be surprised how hard it is to remember a few months later.
But the main mistake I repeat over and over is getting a twist in my binding when I join it up after sewing onto the quilt. Happens nearly every time
Rob