Holding a grudge - hanging onto past hurt with the intention of, some day, some how, inflicting pain on the person who hurt you, by way of retribution - does most damage to the person holding it!
When you hold a grudge, anger, bitterness and resentment eat away at your soul, while the person who caused such feelings to surface, appears to be unaffected. Of course, that makes it worse and you end up in a vicious circle of negativity that was damages you much more than the 'sin' against you ever could.
Whoever tagged the words 'and forget' onto the word 'forgive' didn't do any favours for forgiveness! It is neither possible - nor healthy - to forget when somebody has hurt you. In the same was as your body carries the scars of old injuries, your soul carries the reminders of the wounds inflicted upon it.
You cannot forget - but you certainly can forgive.
In fact, until you forgive the person who hurt you, the pain will never leave and the wound will never heal, simply because you are keeping it open.
Forgiving doesn't mean condoning or in any way justifying a wrongdoing.
It simply means accepting that everybody makes mistakes and people get hurt and that making mistakes does not make any of us bad. It just means we're human.
The old saying that you can hate the sin and still love the sinner explains this very well.
It is the people closest to us, the people we care for the most, who have the greatest power to hurt us. When they let us down, or disappoint us, or cheat and lie and behave in a way that we find unacceptable, they have broken a subtle bond of trust - and that's what hurts!
The only way to really heal that hurt is to go as far as possible to rebuild that bond and the very first step on that road is to forgive the person who caused the pain.
Until that happens, you are caught in an unwholesome spiral of negative emotions and nothing can get better.
If you're happy being miserable, carry on. But, if you would like to feel whole again, start by just considering the possibility that it might be possible to forgive the person who has hurt you.
That's a huge, huge step forward - and the only one you need to take to begin the journey to forgiveness.

Author's Bio: 

Full time writer, teacher, speaker and Mammy with a life-long and ever-growing passion for helping people realise their beauty and potential