Very often in life, anger and bitterness can accumulate in a person's mind, because they remember all the bad deeds that were done to them. Sometimes they feel they are not respected. Other times they feel rejected socially. Well, an answer to this problem can be found in the Christian Bible. If I can recall correctly, the story of Joseph can be found near the end of Genesis Just before Exodus.
In the story Joseph, a Man with 11 brothers became the favourite of the family and was given a coat that contained lots of different coloured fabrics. His siblings became jealous of him and tried to kill him but decided to sell him off as a slave instead. He was betrayed by his brothers.
Joseph was able to overcome his bitterness by praying and doing everything very well. He did everything very well, even though the work he was doing was exploitation.
He was able to forgive his brothers and all the people that betrayed him. I think that bitterness and hate is poisonous to the mind and cuts people off from God. Forgiveness is hard for a human but when they pray to focus on what they are doing , the hate and bitterness goes away.