Please dont give up. If you could post some pics of what you are having trouble with, you will get some gentle guidance here as to how to fix it or if it even needs to be fixed. Sometimes we are way too critical of our own work. Being a perfectionist is tough.
There are a few tried and true tricks to cutting accurately, sewing accurately, lining up seams, etc. that you only learn by doing and with the mentoring of an experienced person. We have all made mistakes and we have all learned from others. It just takes patience, time and a little guidance.
Come on show us whats bugging you.