It's been 5 months since my ex and I broke up; and I know that knowing that this was our first relationship with the two of us, we were emotionally immature and I regret a little bit that I did not act by being more mature and adult (for example when I was not happy with something I kept quiet, instead of calm down and calmly explaining to him what was wrong).

I want to send him a message to tell him how he's doing; but I know I shouldn't do it ... I don't know what to do anymore, I can't get this idea out of my head, it's annoying. Any advice please?