In this verse, Jesus makes a second request in His model prayer for His disciples, often referred to as the Lord's Prayer. It uses terminology that implies debt, but it is intended to refer to wrongdoings. The concept of forgiveness in this verse has nothing to do with the judicial forgiveness of sins by God. When we pray for forgiveness, it implies a reciprocal relationship. It suggests the need to be forgiven of sin by God and to follow God's example by forgiving others as well.
Sometimes, other people sin against us. We are taught to follow the Lord's gracious example of forgiveness in this prayer. It is important to be willing to forgive those who hurt or offended us. Given the immense forgiveness we have received from our Heavenly Father, how much more should we extend forgiveness to those who harm us?
Our relationship with God suffers when we are out of fellowship with others due to unforgiveness. When resentment or unforgiveness fills the heart, it is impossible to maintain the right standing with our Heavenly Father. In fact, a lack of forgiveness impacts both our lives as well as our relationship with the Lord. Thus, let us be quick to forgive others' wrongdoings as our Heavenly Father has graciously forgiven us.

Dear Heavenly Father, although I am a sinner, your kindness has forgiven me through the precious body and blood of your Son, our Lord Jesus Christ. Thank You for teaching us this pattern of prayer by Jesus. Let me be granted a gentle spirit, and help me to forgive all those who have hurt or abused me. It is through Christ that I am forgiven so many things. May I maintain close fellowship with You and be quick to forgive those who sin against me.
In Jesus's name I pray. Amen.