Distractions. Not just those friends’ calls you get to go out in a random moment, but those you create yourself. When you focus on other things, such as painting, studying about stuff you like, watch a comedy movie, or doing any kind of things you like, makes you focus more on what you really want for yourself. Wasting time thinking on negative moments wont usually help. It’s better to think about stuff when you feel better with yourself, and that can be done doing things that you REALLY enjoy.
Also, as @swifting said, thinking about how much will it matter over sort and long periods of time makes you really wonder if it’s worth thinking it so much. Also, act. Sometimes we just overthink stuff because we’re surrounded in a circle of thoughts of “what if” and then “but if I do that, then this will happen”. We get stuck. The best thing to do is just think about the most positive outcome, and even though it could have bad things too, just start acting on it right away.
Talking to other friends (or strangers whom you can vent with in the website) could give you also other perspectives which you haven’t though of, or maybe they had a similar problem that could help you think how would you feel after you’ve made a decision.