Some quilts I just jump right in and start FMQing, figuring out what I'm going to do as I go along. Other quilts may sit sandwiched for a couple of days or more while I'm trying to decide what kind of designs will work best for them. I view "messing up" as an opportunity to go in another direction with the design or perhaps as an opportunity to re-bond with my seam ripper LOL. Anyway, I don't worry about making mistakes--it's just fabric and thread.
Rob