Forgiving can be very difficult. It is a lot easier when the person has repented from their transgression against us. It can be another matter when they are not sorry for mocking, slander or being unkind etc. to us. But Jesus insist on it.
Matthew 18:23-35. Is the parable of the unforgiving servant. Where the king forgives a servants and lets him off paying a very, very large debit, only to find the servant demands a much smaller debt to be paid by his fellow servants. The king finds out about it and becomes furious with the servant and sends him to prison to be tortured, until the debit he owed to the king has been paid.
That parable frightens me. Jesus doesn’t make empty warnings. So how do we go about it? I believe praying for our enemies helps. To pray for their welfare and for their salvation might start out more like a duty at first, but with grace doing this after a while softens our hearts towards them. Keep it up and try to pray with eagerness. When you do the best you can, God will do what you can’t do. If we are too proud to admit we are also a very bad sinner needing forgiveness from God every day ourselves, then we might be tempted not to forgive, which is a serious mistake.
I heard of a story that somebody went to hell escorted by Jesus to show him around. The person saw a women there who was in the ministry for thirty years, but because she refused to forgive her husband she had to read a verse in the Bible about forgiveness as a punishment forever in hell.
Luke 6: 35-36. But you must love your enemies and you must do good things to them and you must lend expecting nothing; then your reward will be great, and you will be children of the Most High, because He is kind to the ungrateful and evil. You must become compassionate, even just as your Father is compassionate.
Loving our enemies is what makes us different from other religions. God is a God of unconditional love. To please Him we need to grow in love and be like Our Heavenly Father. It’s what makes our religion so special apart from being the true religion. God forgives those who are sorry for their sins, doesn’t matter how grievous they are. He loves us all whether we deserve it or not. Matter of fact nobody actually deserves His love at all. He is so Holy and majestic we all fall short of His glory.