All of us want others to forgive us when we wrong them, but we do not always find it easy to forgive others for the wrongs they commit against us. In this verse, the Greek word for forgiving means to be gracious to a person, to pardon him or her for some wrong done. Note that the person has done wrong; they have hurt and caused us pain. But the command is to forgive them.
The reason we are to forgive each other is because God has forgiven us. No matter how much a person has done against us, it does not come close to what we have done against God. Yet, God has forgiven us. Why? For Christ's sake. Jesus Christ died for us - died for our sins so that we could be forgiven. Therefore, God forgives us despite our having rejected, cursed, ignored, and neglected Him.
Because of what Christ has done for us, we should forgive others no matter what they have done. Realizing this truth, letting it settle deep in our hearts, is the secret to forgiving.