"Sukhadukhe same kritva labhalabhau jayajayau"
"tato yuddayayujyaasva naivam papamavapsasi"
Treating alike pleasure and pain, gain and loss, victory and defeat, engage yourself in the battle.
“Duhkhesvanudvignamanah sukhesu vigatasprhah vitaragabhayakroddhah sthitadhirmunirucyate”
Geeta ch 2 
He whose mind remains unperturbed in sorrows, who does not crave for pleasure, and who is free from passion , fear and anger is called the sage of stable wisdom.
Hence Shri Krishna explains that the man of wisdom remains unperturbed because the aim of life is to discharge his duty to the best of his ability. So he always remains happy. He should remain stable in opposite circumstances.
We all are children of GOD. As the parent loves his or her child, what so ever the quality of child is. SO is the God, and since we are brothers and sisters, should love each other in any circumstance. There should be no place for HATE. The God has given the massage to remain stable, and we being children of God confess in front of god, expecting the God to forgive us and love us with full heart. GOD also gives message to all his children to love each other forgiving and forgetting their mistakes.
In the contrary when we get hurt by someone, we do not try to forget, and start hating the person. We try to make a point not to forgive him in our life time and continue to hate him.
'Between the HATER and the HATED, it is always the hater who gets hurt more. Every negative emotion secrets acid in your body, and acid destroys the vessels, which contains it. Anger, frustration and disappointment are visiting emotions. HATRED is a progressive negative emotion. The hurt you suffered from an event is insignificant, compared to how much you keep intensifying the hurt by repeatedly reprocessing what had happened or what was done to you .
Hatred takes you away from your real you. The 'hatred' now becomes the HERO of your mind and heart, literally remote controlling how you feel, think and act.
People do what they do because at that point of time it seems to them that it is RIGHT. 'WRONG' is seldom intentional. It is often out of ignorance. They do not know that they DO NOT KNOW.
If you intensify your hatred and decide on an eye for eye reaction, then it becomes REVENGE. People need your love much more when they are wrong then when they are right. Therefore think only GOOD even to those who have not been good to you. Every man will face consequences of this own doing .you do not make yourself wrong to prove that the other is wrong. Forgiveness is not liberating the other from you, but liberating yourself from the other. Something happened to teach you something, learn the lesson and just move on.
SWAMI VIVEKANAND has said "the moment I have realized GOD sitting in the temple of every human body, the moment I start in reverence before every human being and see GOD in him, that moment I am free from bondage, everything that binds vanishes and I am FREE. As said by Swami Vivekananda, "all love is expansion, all selfishness is contraction. Love is therefore, the only LAW of life. He who loves, lives. He who is selfish is dying, therefore love for love's sake, because it is law of life, just as you breathe to live.
Vivekananda also taught to love yourself. According to him 'you cannot believe in GOD until you believe in YOURSELF.
Where can we go to find God if we cannot see him in our own heart and in every living being. The first sign of your becoming religious is that you are becoming CHEERFUL. The age old saying "Hatred cannot be conquered by hatred, it can only be conquered by LOVE"