It's not a failed marriage; it's a chance to learn what you don't want, but more importantly, what you do. It's not a fool-hardy mission; it's a chance to test out what you dream about. It's not wrong, it's just not exactly right. It's not a misstep; it's a redirection. You can't find out where you are going without walking down a few paths taking you where you don't want to go.
Life doesn't have to be perfect. Choices don't always have to be right. Ideas can be better in thought than in reality. But it doesn't mean that any of these are failures. They are opportunities, to reassess and reimagine, to reconsider and revise. Having something that doesn't work out the way you thought it would, allows you the chance to decide if something is what you want, to decide if you want to do something else, to decide if you want to decide something else. Almost nothing is written in stone, and almost nothing is so permanent that it can't be undone.
So give yourself a break. Stop setting impossible standards. Stop berating yourself for perceived mistakes. Instead be proud of yourself for taking a risk. Embrace the fact that you are trying, even if you don't succeed. Look at each step along the way that doesn't work out, not as something to be ashamed of, but as something to learn from. Admiration should be given most to those who will attempt something, even if they don't know the outcome, and less to those who will never take a wrong step because they will not try.