How to get rid of overthinking? 

Figure out how to reach that solution. For example, if your solution is to have two new close friends in the next 4 months, you could look for ways of getting people to trust you, or investigating the possibility of getting closer to some of the people you already know. This step involves collecting any information that will allow you to reach your solution.

Design simple, clearly defined interventions to reach your goal. This are small, simple actions, things that you can do. It could be hosting a party, studying for at least 90 minutes every day, or simply saying hi to your coworkers, depending on what your goal is. The key is that, at the end of the day, you either did what you were supposed to, or didn't. Easy, simple steps.

Execute the interventions. Don’t think; just do. If anything goes wrong, analyze what when wrong and try over.