When you forgive, you have to let go of your feeling of resentment. If you say, you forgive someone and you're not comfortable with and still bringing with you all those bad things that happened in the past, then you're not forgiving that someone, yet. You have to let go all those feelings.
If you are asking how would you that someone has truly forgiven you? It's up to that someone and usually, if that someone has forgiven you in all his/her heart and let go all those resentment, you will feel better as well.