always have a sharp blade. roll the cutter along, you don't need a lot of pressure. actually, one layer is harder to cut because it can slip more easily. are you using the 45mm ruler?
the 60mm is great for several layers but harder to control with only two or one layer. always cut away from you. side cuts, horizontal cuts for the other side, etc. can get you in trouble--not just bad cuts, but dangerous. ruler size to suit cut size is an excellent suggestion. use a 12" long ruler whenever you can, not the 24". practice cutting 1 1/2" strips & then you can use them later on a strip quilt. won't matter if they are a little wonky. I will improve !