i was in a very unenviable position to decide whether or not i should stay and fight to save my relationhsip or to just cut my losses and leave. often love clouds ur judgement and often u do stupid things under the pretense of loving someone.
regardless of the reasons why the relationship is crumbling, u have to decide the best course of action. if both of you can come on to a consensus on what to do next, it would be much better. u both can decide to fight or say goodbye.
now if ur the one doing the leaving, i would suggest u make it abundantly clear to ur partner that nothing they can do would ever be enough to save the relationship. (then u can call ur other boyfriend to get ready la kan)
if ur the one hoping to save the relationship, u need to assess if it is all worth it or not? yes u love them but sometimes love just doesn't cut it. there are issues that needs to be addressed and u need to do a whole lotta convincing, convincing urself most, and of course ur partner too. u need to highlight to them the merits of staying in the relationship. how ur going to be what they always want u to be. how things are going to be different.
having said all that, if their hearts are no longer with u. it will often be futile la.
just let go.
mope for a bit. and then move on.