little late on the breakup thing here but just wanted to say something I think is an interesting insight I had while getting back together with an ex. We were debating getting back together and I said that if you think about it, most of the relationships you ever have in your entire life don't really work out. From people you just meet once and never see again, to your family, to everyone you date, to the person you marry. Most of these actually don't 'work out'. People fight with their family but still keep in touch here and there. You meet a million people in every class, social group, party, etc and yet you see almost none of them again. Everyone you date until you're in a serious relationship or even get married, it doesn't work out with. And even then, when most people are really really sure it's perfect, they get married, and shit 50% of those people end up divorced. So not to make it depressing, just realistic, that in a way, we hope, we dream, we believe, that everyone we meet presents an opportunity for a meaningful long-term fulfilling relationship (friend, sexual, etc) but for the most part they don't really happen that way. Doesn't mean don't try, but if it doesn't work it's actually more likely given the odds and it's ok to fight a bit for it but eventually move onwards and upwards.
I feel like the only way a relationship stops working is if you both give up on trying to make it work out.