It's easy to be good to people who are good to us. But what about when a coworker does things to keep you from a promotion, or a friend betrays you, or a relative isn't honest with you in a business deal, or somebody says something about you that isn't true? It's easy to get bitter, hold a grudge, talk bad about them, and think about how you can get even with them.
But Jesus said, "Love your enemies, do good to those who hate you, bless those who curse you, pray for those who mistreat you" (Luke 6:27–28 NIV). Why would He say that when they don't deserve it? Because you're not blessing them for their sake, but for your sake. Life is too short to go through it with bitterness poisoning your life. If you'll let go of the hurt they inflicted and live out of a place of forgiveness, out of a place of wholeness, you'll not only feel better, but that's what allows the Creator of the universe to go to work and take you higher.
This is what Joseph did. His brothers sold him into slavery that led to thirteen years of immeasurable suffering, heartache and pain. Yet after Joseph was made second in command of all of Egypt, and when those same brothers came before him looking for food, he didn't say, "Thank You, Lord, for payback time!" The reason God could promote Joseph to that level is because He could trust Joseph to handle the power correctly and be good to people who had not been good to him. Instead of paying them back, Genesis 45 says that Joseph wept, embraced and kissed them, and invited them into the palace. He gave them food and land and took care of his entire family.
Give people the grace to change. Don't judge their whole life on one season, one mistake. The mercy you show others is the mercy God's going to show you. If you're bitter and angry, you'll get stuck. I'm not saying you have to befriend them and allow them all access, but you need to get to the point where you let go of the offense and treat them with respect; you're good to them, you're kind. Be a Joseph. Let God pay back the people who hurt you. You're not the judge and jury. Leave it in God's hands.