Forgiveness is a part of life. It's not optional; it's something we ought to do. The Bible says: "Bear with each other, and forgive each other. If someone does wrong to you, forgive that person because the Lord forgave you." Colossians 3:13 NCV
Some think that the people who hurt us so deeply can ever attain a place of forgiveness in their heart. But look at it from the other perspective, you must have also hurt someone at some point in your life. When you summoned the courage not only to realize your wrongdoing but to even ask for forgiveness, how did it feel after the other person accepted your apology? Didn't you feel relieved?
Some people use the approach of "I will forgive, but I won't forget." Can that be real forgiveness? Wouldn't anytime you remember what the other person did to you, make the negative feelings associated with that incident resurface? Then, how could you have forgiven if you still have some resentment in your heart towards that particular incident or person? some might argue that not forgetting will keep you alert and on guard; but shouldn't you always be? Holding on to grudges towards another person won't keep you on your toes but only in a place of negativity. Developing a mindset that will allow you to discern who is for you and who isn't is the key. And that won't be achieved through being unforgiving but through meditation and taking note of the lessons learned.
Not forgiving another person is similar to being in bondage - in essence, you give another person power over you by allowing them to navigate how you feel. Even if you want to, the fact is anytime you hold on to the wrongdoing someone has done to you; you have negative feelings about it every time it comes to your mind. Allow God to take that burden off you. It may be hard, challenging, sometimes may even seem like the impossible thing to do but there is freedom and love in forgiving others. If others have forgiven you in the past and God forgave you your trespasses, you should do the same.