I know firsthand about the effect on endorphins and being active on self esteem.
In adult life, there have been 4 times when I was in a very bad state emotionally. One when I was 26, one when I was in my early thirties, one when I was 40 and one last year.
All but one of these times I was drawn to something active and pulled out of it in that way. When I was 26 it was karate (I got up to brown belt); when I was in my early thirties it was competitive race walking. And last year it was hiking and volleyball. The one when I was 40 was different because of the nature of that "low point" in my life. I was physically unable to be active for some time - I had been in the hospital for a week, listed in critical condition, and nearly died. I also had two (for completely different conditions) surgeries that year, only three months apart.
I started thinking of this when the posts here started talking about sports and being active and the effect on self esteem. Apparently when I have tough times in my life and my self esteem plummets, I also become more interested in sports and being active, and that's how I pull myself out of the blue funk I'm in.
Unfortunately, this seems to be lost on many of the people where I am originally from - if a woman is athletic, men won't have anything to do with her. I have not found that to be the case in the cities I have lived in though, just in the rural area/small town where I grew up.