I read in a post, smile to yourself in front of the mirror daily.

You need to see if a distraction can help when negativity happens. A distraction could be a game here at PC, any game you have access to, music you enjoy, anything that you enjoy doing.

Try to think of reachable goals. For example, to clean up your room or one part of your room. When you reach the goal, think positive thoughts. If you do better in one day than another you get an idea of how you are. If you busy doing goal setting and reaching the goals, then you are occupied with the task at hand and you have passed that bad period very quickly.

Idk they are suggestions and hope it helps!