One main question that may go through your head is, "Is it my fault?"
There are always going to be events or situations that may lean more towards your fault, but do not let that discourage you or crush you even more, thinking that you could've changed the outcome by your actions. The truth is, there is no one to blame if you look at the big picture. Things either work out or they don't. That's life. Whether it seems like it happened because of your actions or your past partner's actions, you shouldn't put that fault on yourself or them. If things didn't work out, it would've happened eventually no matter what. Think of it as a gift from God: the sooner you get let off, the less attached you are.
The healthy thing to do is to accept the break-up as a mutual agreement, as if it was no one's fault specifically, no matter how heartbroken you are. You will find that more opportunities will cross your path and there will be more opportunities for happiness for yourself and your ex. You can't lie to yourself and say that you don't want nothing but happiness for the one you love, so overall, this is what's best for the both of you. If you can tell yourself that and believe it, you're that much closer to healing your broken heart. Being selfish in love will get you nowhere.