there are 4 elements to improving your mood: relaxation, stress management, cognitive control, and exercise (RECS for short). and I think people who struggle to do so don't realize they're focusing too much on one area, or aren't doing them effectively.
like as my therapist told me, using your phone or watching TV to relax doesn't really work because your brain is still "on" and processing a shit ton of information, or doesn't really engage your mind while still requiring concentration.
me personally, I think I wind up relying on cognitive control to tackle emotions instead of addressing them in the other ways.
here's how to do your RECS:
Relax: Read, write, listening to calming music (but don't rely solely on this! and don't listen constantly) going into nature or a park, meditation, puzzles
Exercise: walking, yoga, weight lifting, dance, gardening, cleaning the house
Cognitive control: self control/stop & think, self monitoring/evaluation, emotional control/managing feelings, flexibility, task initiation, organising, planning (and the things they teach you in CBT)
Stress management: breathing exercises, progressive muscle relaxation, talking/venting
you can pick one from each and see how they affect you when you’re feeling a strong emotion, you might need different techniques for different emotions.