Many people are feeling worthless and burdened because of overthinking. Keep yourself occupied and busy with some kind of the work or other. Whenever you find yourself overthinking, just divert your attention to something else. Read some book/novel or watch some movie or show on television or even do some walking exercise. You can even pursue some hobby like drawing, painting, writing poetry, composing music etc.
I once had this overthinking problem and couldn't handle myself well. It lead to depression and other mental illnesses. It took a lot of time for me (years in my case, but it need not be the case with everyone) to overcome this problem. It's not easy to come out of this problem, but if you put sincere efforts, you will definitely succeed.
Replace negative thoughts with positive ones. Think about the good memories you had experienced in the past. Keep your mind active by having some goals for yourself. If you don't have any goals till now, its never too late - frame some goals. Make a plan to achieve them.
One good news is once our mind gets into a habit of positive thinking, it would never like to go back to negative thinking. So cheer up and take charge of your life. All The Best.