When it comes to relationship breakups before and after, there are two questions that need answering. "Why?" and "What's next?"
There is no doubt that dealing with relationship breakups before and after they happen, is a very traumatic and stressful time. It doesn't matter whether you were ready for the relationship to end or not, when it comes to a relationship ending there is still the same trauma, still the same upset.
Now, if your relationship hasn't actually ended yet, but it's on the verge of ending, then make sure you do your best to go through the coming days, weeks and months with as little drama as you can possibly manage. One of the classic mistakes that many people make, when faced with an imminent breakup, is to cause drama and upset. This is an understandable reaction, because they're upset and devastated at the ending of a relationship that they put so much hope into. However, control is key, especially if you have any hopes of rekindling your relationship in the future. Causing ructions and drama at the onset of the breakup will not help you further down the line.
So in regards to relationship breakups before and after, even if you're not ready for the relationship to end, agree to the breakup. Let your partner go and wish them well. Tell them that you're sorry for any mistakes you have made and that you wish you could've done things differently, but you accept their decision to end the relationship.
Something else that you should consider in answer to the "Why?" question is this: even if you have no interest in trying to rekindle the relationship, it might still be worthwhile exploring why the relationship ended. Answering this question is really a positive step forward for you and for any future relationship that you may enter.
Look closely at your behavior throughout the relationship. Try and pinpoint moments and incidences where you felt you could've handled the situation better. Be as honest with yourself as possible. If you and your ex have parted on fairly good terms then why not ask your ex how they felt you handled yourself in the relationship. Not only will this give you some great insight into how others/your ex sees you, but again, it's good food for thought for the future.
For some, when it comes to relationship breakups before and after, a wise move is to move on. Let's be honest, not all relationships are worth saving. For a variety of reasons, some relationships are just better over and done with. If you think your relationship falls into this category, then After the breakup give yourself as much time as you need to grieve the end of your relationship and then do just that, move on!