I am struggling to give a good answer to this since some minutes...

There is no special trick. I just realized that it makes no sense to worry about stuff I can not influence. And that if I have bad mood without obvious reason.. I could have good mood without obvious reason as well.

I have no step by step instruction. It is just a decision you have to make for yourself.

Focus on the good things instead on the bad. No matter how big you fuck up, chances are very high that you are still better off than most people on this planet.