You sound like me. My hand always seems to move when I am cutting a long piece. First of all, the rotary cutters. I recently purchased a Fiskar Titanium cutter. It is great! Cuts much more smoothly and the pressure can be adjusted. I can cut through many more layers without having to go back over it so many times that I then have frayed edges! I got it at Joann's with a coupon. It was only a dollar more than the regular rotary cutter and I recommend it highly. The next issue, I was cutting fabric at my mentor's house last week and noticed nothing moves with her rulers. She has these sticky dots she buys and puts on the back (downside) of her rulers. They hold very well and no movement for me. I came home and put "double sided scotch tape" on my rulers and now nothing is moving. Try that and see how it works and good luck.