This is not about sulking over past relationships and how bad it was or shitty partners. Its about the relation with our break up. Now this needn’t necessarily concern a partner. It could be anything like work, parents, passion, hobby, dream, pet, sex, love etc.
How well is our relation with our breakup?
Is it making us happy?
Do we need to consider reconcile?
Is our co-existence natural/necessary?
Breakups are mostly overwhelming and consuming and its okay to be devastated and miserable during the process. Only when you acknowledge and exaggerate the severity of the situation, you can begin to heal because “the only way out is in”.
My way of coping has always been extremely dramatic and I try to humor myself even while crying. About crying, I think its most important part because once you are done you are exhausted and have a head ache, just in that moment you think if all this is worth it? And instead of over thinking you sleep.
The best part is yet to come. Once you start accepting that breakups are inevitable, you stop being afraid. You will plunge into any hopeless relation, just to see where it takes you. It could be with a pet, who most likely will not out live you (if you are lucky, that is how messed up this relation is) 
The best example is our fear of dying which we know is a harsh reality. I personally don't like to predict my afterlife and I strongly deny the existence of hell/heaven altogether, similarly I don't like to imagine how my life will be without someone or something. I instead focus on what I have and to make it beautiful until it lasts.