Take it slow Tim, as they say measure twice, cut once...
It takes a little practice. I’m not a great sewist but I’ve made a couple of things I’m proud of.
I hear you! When I am making a violin or cello, I measure at least 10 times, then I do a practice cut and test the fit. Being new to this there is an element of hurry and rush and learn and feed the brain.. heck it is nice to feel that and I am "allowing" myself to be the kid in a candy store for the moment. But as in the practice cuts, I am throwing everything I have at scrap materials and such, so as to make a few mistakes, since it seems I learn by making mistakes. I craft once I conquer the mistake. So it is going to be a long time before I know I will be crafting. Until that time YOU (The Forum) have to put up with me posting mistakes and horrible looking oops. Forgive me but I do think it is good to share the ugly learning part, that maybe someone out there could benefit from that. But I will amend my attitude a bit as when it comes to safety, I put the kid away and weigh my approach carefully. (Now to find a seam ripper to free my fingers from each other)
This has been a fun day, Thank you to everyone for this.
Tim