As imperfect human beings, when receiving a bad gesture, offenses, to be deceitful, defamed by other people or in short someone pays us badly after having done a good, we always feel in our heart a deep pain, disappointment, anger, feelings that they are born from the heart and that if we let these feelings drag us, we will end up doing bad things. More than a Christian person or not, has fallen into an "eye for an eye" and "tooth for a tooth", taking revenge for themselves.
What does God say about this?
Romans 12: 17-21 Reina-Valera 1960 (RVR1960)
17 Pay no man evil for evil; seek what is good in the sight of all men.
18 If possible, as far as it depends on you, be at peace with all men.
19 Do not avenge yourselves, my beloved, but leave room for the wrath of God; because it is written: Mine is revenge, I will pay, says the Lord.
20 So, if your enemy is hungry, feed him; If he is thirsty, give him a drink; for by doing this, embers of fire will heap on your head.
21 Do not be overcome by evil, but overcome evil with good.
This is what we must do in these situations. As children of God we must always have the identity of the Father and our Father is love.
Although we know that doing good when they do us wrong, it is not easy ...
How can we achieve it?
Source
Dying to our flesh and with the help of the Holy Spirit. The Holy Spirit is our helper, he is the only one capable of drawing goodness and love from us; but we must renounce our own thoughts and desires and be willing for Him to change us and help us, let Him act in our hearts as He wants to act, because the Holy Spirit knows us more than we know ourselves and knows in which area to work.
Do good no matter how badly they pay you, just love! Remember that if you pay bad for bad, you put yourself on the same level as you do bad, that is, you would be the same as that person. On the other hand, if you always do good, God's blessings will persecute you, you will reach a good opinion before God and men, and your enemies will be ashamed because of their evil.