Praying for someone when they treat us badly is not usually our first reaction. However, that’s what Jesus encourages us to do. The term "bless" is derived from the Greek word eulogies, which can also be translated as "pray for." Jesus asks us not only to forgive those who sin against us (Matthew 6:14) but also to pray for them. How can we pray for someone's well-being when they do or say horrible things to us that make our lives miserable? With our limited human understanding and strength, it is impossible. But we can do anything if we have God's great love in our hearts.
When we hold grudges against others, our hearts are troubled. We cannot control other people, but we can choose how we react. When we pray for and bless people who harm us, we help them, as well as ourselves. Rather than allowing others to hurt us, we can choose to forgive them and ask God to help them! When we treat others with such love, God sees, and He will reward us with perfect peace in our hearts, mind, and soul.

Dear Heavenly Father, please help me release my anger towards those who mistreat me and replace it with Your perfect love and peace in my heart. I know You brought those enemies into my life for a reason - to make me stronger. I pray You to fill their hearts with peace and guide them to Your way of living. I refuse to fall into the trap of sin and instead choose to praise You by being kind and loving to others. 
In Jesus's name I pray. Amen.