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.
That's good ideas actually many people see this as normal thing to occur to human but it's been generated by so much unrealistic things that can never have their ways in your life leads to the problem of over thinking, the best is to eliminate any thoughts that is contrary to your life agenda, don't involved in too many tasks that may seem unfinished by you all this can speedy the elimination of over thinking.