Working out. Either biking, walking, lifting weights, doing martial arts, etc. It doesn't matter. In some of my lowest points if my life I started working out and it helped. It didn't fix it but it really helped my mood improve. It also raises your self-esteem. I did a couple of years of BJJ and it really made me feel better about myself. Now I go to the gym and lift weights. Looking better and seeing the weights I can lift become heavier do a lot of me.

Music. Pick up a guitar. Thomann sells really cheap guitars that are great for beginners. Learn some songs you love and play along with them. Just look up tabs online and go from there. Eventually, you'll realize that you can use the instrument as a constructive channel to your emotions.

Both (or even most) suggestions you're going to hear about this topic take discipline. There is a reason for that. These things are rewarding proportional to the effort you put in. Seeing yourself improve at whatever you choose ultimately will only happen when you make the time and put in the effort. Do not be discouraged. The first few weeks are always hard but you can build good habits in a short time.