When you realize just how much that you have been forgiven.
By Christ as well as many people in your live here on the earth.
Then you begin to start forgiving others as well for its only right.
To hang on to your unforgiveness can actually be selfish to an extent.
While others just do not know how to forgive because they been hurt so much.
But in order to receive Gods love in its fullness we need to forgive.
Not always for the other person sake but for our own sake.
Because most of the time the other person doesn't even know.
So please pray for Christ to teach you how to learn to forgive others.