Forgiveness is by far one of the most important skills a person can have. Being able to forgive is a personality trait that is crucial to one's own happiness and their relationships with others.
The first thing is being able to forgive yourself, but even more important is being able to move on when it comes to others. Moving on could mean talking out your problems or coming to terms with the way your relationships are now. That doesn't mean ignoring the issue or justifying the wrongs, but learning to move forward. I'm not saying it's okay to let people walk all over you if you forgive too easily, but being able to forgive is an instant way to live a happier life.
This is easier said than done because it seems easier to stay mad. It's healthy to rant to your friends and get your feelings out. But with our media-based society, people tend to air everything on social media platforms like finstas. This habit just instigates negative feelings and heightens anger from both parties even more. Instead, it's important to not let emotions dictate your actions, and focus on letting go.
Another thing to keep in mind is that forgiveness doesn't mean pushing the problem aside. It's important to address the issue so you're not holding onto grudges. Growing up I've seen too many family relations strained by past issues that still come up. My family's dynamic of being distant from my relatives has opened my eyes. Going forward that's not the way I want to live my life, which is partly why I feel so strongly about forgiveness. No matter what problems arise, you have to be able to take a step back and see both sides.
Once you do this, it's so much easier to confront the issues in a productive way. Sometimes relationships won't always be the same as they once were, but if you keep a calm head and do all you can to move past it, you'll be at peace with the way things work out.