Originally Posted by Murphy224

All the hints you have received are great.....a good ruler that doesn't slide on the fabric, a weight to hold down the end if you are using a long ruler, keeping part of your hand on the fabric and part on the ruler to hold it steady. But the best thing that helped me with the issues you are having, was to slow down! Those people on the you tube videos just place their ruler, put that cutter in place, and zoom off. Zip zip zip and they are done! You don't have to do it that way. Just slow down a bit, press firmly but not so much that it won't move with the cutter, and go only as far as your arm will go comfortably. Once I slowed down a bit, my ruler didn't slide and I didn't get away from the edge of the ruler. I focused on what I was doing and felt safer and more in control of the rotary. I also fold my fabric and use my 6x12 Creative Grids ruler most of the time.
Good luck! And remember, you will get better with practice.