Overthinking somewhere leads to depression and anxiety. Without thinking, depression is just a feeling of down-ness or lethargy or sadness with no label, with no link between any of these things. You have some feeling that you don’t feel like doing anything, and you don’t give it some grandiose label such as depression that contextualizes it in this larger life narrative. You’re simply lethargic and you do with that as you will.

And the best solution for it is to control over own mind. It sure can. It all comes down to controling your thoughts. If you have an overactive mind you should always try to keep it busy buy reading about unrelated subjects (works best for me). You should also keep in mind that thinking about something constantly will not solve the problem because it will only lead to more stress and confusion. This is especially hard when you have a big problem but what I’ve learned over time is that the first solutions that came to mind were the best, overthinking only made it worse.

This article is all about Overthinking 

https://buddingpsychologists.org/how-overthinking-can-ruins-everything/

I found it really useful and informative.