One thing I did before is every morning, I list down at least 10 things that I am thankful for the day before. It trains my brain to have that positive mental attitude. Moreover, it helps me to reflect that there are many good things happening around me, I just need to have the eye to see and ears to listen.
This is good.
If this really helps you, keep on doing that. This is a gesture of being grateful to what you have and that counter the thoughts of being an overthinker.
Keep on practicing this and soon even you have no list at all, you'd be grateful by just even waking up in the morning and let the day work on its own without having to worry.