Forgiveness does not change the past, but it does enlarge the future.
How often do we forgive? Is it every time that someone does something unkind against us? Or do we rather hold the grunge? Think about the whole situation over and over again, feed the hate and other negative feelings? Truth is that forgiveness is not only letting go of the bad feeling towards the person who did something that upsets us. It is mostly to make us feel better, letting go of the negative emotions, letting the past staying in the past. It calms us down and gives a better light for the future. So lets practice it more often.