According to an article published by the Mayo Clinic the author states, "Letting go of grudges and bitterness can make way for compassion, kindness and peace." It further says that giving forgiveness can lead to:
Greater spiritual and psychological well-being.
Less anxiety, stress and hostility
Lower blood pressure
Fewer symptoms of depression
Lower risk of alcohol and substance abuse." End Mayo.
Dwelling with a sense of injustice toward you leads to the emotions Paul identifies in Ephesians 4:31-32: bitterness, wrath (lifestyle of anger) flashes of anger, clamour (meaning loud insulting language demanding rights, etc), and evil speaking. The verse further implores the getting rid of all malice. The opposite attitudes to be sought after are in verse 32. The context strongly suggests that the key to enjoying the correct attitudes is dependent on forgiving the offending person.
A Study by Hope College, Holland, MI states:
"Nursing a grudge is hard on your body. Researchers asked volunteers to think about a time someone had hurt them. When prompted to dwell on their resentment, subjects showed greater physiological and emotional stress-higher blood pressure, heart rate, perspiration, and intense facial expressions."
My book, Outrageous Forgiveness In 30 Days may help you understand and gain victory in this area.
Ephesians 4:32 And be ye kind one to another, tenderhearted, forgiving one another, even as God for Christ's sake hath forgiven you.