Experience is only gained by doing. Some people make wonky quilts on purpose. I liked the idea of adding sashing. As long as you have tried, that is what is important. Pictures would help us to help you. See if there is anything you can salvage. I'd keep the fabric awhile to see if you later get an idea how to use it. For your next project, choose a simpler pattern. Each project you successfully complete is one more step up the ladder, and you will learn something with each one. Do not criticize yourself. At least you are making an effort.