You have to come to a base understanding that everything is temporary. This will eliminate a big majority of the things you stress about, that are really not worth at all.

And for the things that make you stressed for a good fucking reason, well, you should think strategically if you want to get over that situation. You will not function well under stress.

Stress is just your mind torturing yourself, nothing else causes stress. Seperate reality and your mind to look at the picture from outside. Then everything will be more clear and you will be stress-free.

Until you forget that fact and get yourself stressed for no reason in a week