A grudge is a heavy burden to carry.
Let it go.
Bottling and holding onto frustrations over what somebody else did to you is wasted energy and self-inflicted suffering.
Building a big life is hard.
Becoming a person of true greatness is hard.
Don't make it harder on yourself.
Learn to forgive and move on.
We all make mistakes.
...and if you'd like to be offered the same grace and forgiveness for the mistakes you make...
You have to forgive others for theirs.
No matter who it is...
No matter what they did...
Offer your forgiveness.
The only other option you have is to continue obsessing over what happened instead of using that same time and energy in a healthy and productive way.
What's it gonna be?
The choice seems pretty obvious to me.