I think there's a lot to be said for changing your appearance as part of the process of improving your self-image. It's a fairly straightforward, quick and easy method of making yourself more like the sort of person you want to be. It's good for a quick jolt of self-esteem and it can help catalyse other changes to make you feel better about yourself.

However, you do have to view it as part of a process, or it doesn't actually accomplish anything. If all you're doing is a one-off change of appearance to try to feel better about yourself, then you likely have other, bigger problems that need tackling as well.