I love my rotary cutter also. The best advice I could give is to TAKE YOUR TIME and pay strict attention to what you are doing. Once you and your cutter develop a relationship and you trust each other you, too, will love your rotary cutter. Its a wonderful tool ... you just need to have a healthy respect for its power.
Also, be sure to use the same ruler to cut an entire quilt. Surprisingly, rulers sometimes differ slightly in measurement, and just that slight difference could throw your quilt off.