I don't know about manly advice (I only just survived puberty my self, finished last week some time (I hope)).
I know it is an annoying word but believe it or not puberty is real and it lasts longer for guys then girls. Girls are different, but for guys it makes us feel aggressive, intolerant and insecure (amongst other things). It sounds a bit like your "Cage Fighter" is suffering from the aggressive, intolerant and insecure bit at the moment.
Having said that, I don't actually give advice but I can tell you a few things I did when I was in your sort of situation and age that made it worse (and I did these more then once) and what I think I should have done.
1. Sleep with the girl (or start going out with her or whatever it is called in England these days). This always ended badly for me, in fact it happened with my first "Girlfriend". It just ends badly, a relationship that is started badly in my experience usually ends badly.
2. Confront the guy (Read above about puberty). While I managed to beat the shit out of a few guys with my spastic teenage fighting stile (Imagine an angry windmill that cannot be damaged, I a not saying yours is, mine was though) I also took a few beatings myself and in the end there was no real outcome, we were just a few idiots fighting over what should be nothing and making sure that the girl would be friends with nether of us.
3. Confront the Girl. I know it may seem like a good idea, but the only time (1) either she or I brought it up is the only time I actually managed to keep a friendship is that I appeared noncholont about the whole deal.
4. Puppy love does not exist! Sorry, but it does with all the hormones that were flowing around my body when I was a teen all a girl had to do is smell nice and I was in love, the boyfriend has the same feeling by the sounds.
So those are my mistakes, here is my single success;-
The one time it did work out for me was when I pretended that I did not care and I eventually became best of friends with her and the Boyfriend (Him later on), they eventually split up though and both are Married now (to other people) and have children (with other people, obviously) but I am still in regular contact with both and while they live 3,000 km apart (In opposite directions from me) I quite often have them visit, even a few times at the same time (We have a ball, we talk about how stupid we one were (I do think his wife is hot though.... shudup nerf
)).
I know it is hard Krizz, I have been there.
Nerf
: lol wht u mean?
