Bitterness is a part of a person's persona. If someone allows the bitterness to be the overriding emotion in a breakdown of a relationship, it's a harder trait to recover from. A harder place to move forward from. It is hard to not take personally that a person has not only betrayed you but has taken either money, statute, or a close friend with them.
The worse feeling ever is when friends betray you with their love for each other. That's a hard one to come back from. So bitterness and anger, as well as loss and loneliness are are all valid feelings after the break up of a romantic relationship.
I don't think one can rush the recovery from this relationship. So, bitterness needs other emotions to equal it out. Trust, friendship, and a belief that love can happen again. It's only time that can heal the bitterness - but sadly I see too many people that hold their bitterness and anger so close for so long that they are unable to believe in love again.
Many of us are holding onto bitterness as a way to ‘do something’ about what was done to us. We are wanting justice or vengeance for what was done to us. I get it, we want to hurt them for what they did to us. Because it seems like they are ‘getting away with it’ if I let this wrong go. But is responding this way to a hurt done to you helping you or just keeping you entrapped to feelings of anger, resentment, and hurt?
Being entrapped in bitterness is a vicious cycle that is hard to let go of. Some people don’t get over it and remain bitter and some don’t get bitter. They get better: they learn from their mistakes and don’t repeat them. They know themselves well enough to know who will be a good match for them and don’t settle until they find that person.