This is an excellent question. Let me give you a few points that are essential to any discussion on forgiveness from a Christian perspective.
First, when discussing forgiveness, you should speak of the forgiveness of God. In fact, all forms of forgiveness flow from the forgiveness of God. In other words, we are able to forgive one another, because God has forgiven us in Christ. This one of the basic points of the Bible. Remember the Lord's prayer - "Forgive us our trespasses as we forgive those who trespassed against us."
Second, we also need to consider the cost of forgiveness. According to Christianity, forgiveness was not a simple matter of the will or something that was easy to do. Quite the contrary, forgiveness is only possible, because God sent his son, Jesus to die on the cross for the forgiveness of sins. In light of this, we can say that forgiveness was extremely costly. Here is what Paul says in 2 Corinthians 5:21:
"God made him who knew no sin to become sin on our behalf that we might become the righteousness of God."
Third, to have forgiveness, a person needs to take the first step, namely to acknowledge sin and ask for forgiveness.