Often relationships produce some significant hurt. For example, I don't know how people who get divorced survive the hurt that must bring? Yet, in all relationships, there are levels of hurt that occur. Significant hurt due to betrayal, dishonesty, cheating, and abuse is hard to get over. For example, you expect a good friend to be honest, but then when you find they are dishonest, you become greatly hurt. How do you get past that? Or a friend that you supported deeply for a long time, turns on you in a vicious and hurtful way? How do you move past that?
Understanding why a loved one hurt you is one step in the right direction when it comes to getting past the hurt. For example, if a friend is hurt themselves by a life event or a person's lack of consideration, that friend may lash out and hurt others. Understanding the root cause of a person's hurtful behavior brings empathy, compassion, and understanding which can defray the hurt. However that doesn't mean you have to subject yourself to the hurtful behaviors. What it does mean is that you may need to have a conversation with your friend about why they hurt you and what you both might do in the future to avoid that kind of hurt.
Also being hurt helps you to understand what behaviors do hurt others and that may help you to avoid similar behaviors with friends. Being hurt lets you know how painful that is, and that pain teaches you not to do the same thing to others.
It takes time for hurt to dissipate. The greater the hurt, the more time it takes. But in time, hurt mostly goes away and softens in ways that don't drag you down anymore and this is a good thing. Onward.