capable of being justified; that can be shown to be or can be defended as being just, right, or warranted; defensible: justifiable homicide.
the feeling of displeasure or indignation at some act, remark, person, etc., regarded as causing injury or insult.
Think about it. Do you have someone that you justifiably resent? Do you have a good case that says "but you don't realize what they have done to me~"... or "you don't know how they have ruined my life?"
Jesus looks on us with mercy and grace. It does not matter what we have done, and believe me, what we have done to Him is worse than what others have done to us. Yet, He forgives. He is pure love.
What a dangerous place to be in our thoughts.
Forgiveness does not warrant deservability. It warrents loving the way that Jesus loves.
Forgive that person today. Let it go. Don't go back to it.. don't fan the flames... just put it in the hands of the One who gave His life for you.