It may be also that you are too hesitant because it is so new to you. I watched my sister use her rotary cutter with such confidence whenI first started, and I was terrified. I often let her cut my fabric for me.
But it was lack of experience. Or at least I am now confident enough that I rarely have problems. Maybe you should practice on fabric that isn't something you care about?
Anyway, with experience....and a sharp blade...you will do fine.