Baby steps. Not sure by your message why you feel you will cut everything wrong, perhaps the whole cutting out process is overwhelming for you? Baby steps. Take your list of cutting requirements, and one color of your fabric and make all the cuts for that one fabric today. Then step away, be happy with your accomplishment, make a checkmark next to your cuts made on your list and start again another day.
I find most of my mistakes made are when I'm tired, and just want to get it done.