How can I get rid of too much resentment in my heart?

I think you can choose to do some intense exercise when you are particularly excited. Learning yoga in peacetime can help you adjust your mood, make you feel calm, exercise and keep fit. You can also travel, preferably to places with mountains and water, get close to nature, and you will gradually feel peaceful. You can also listen to some soothing and brisk songs at ordinary times, feel the happiness around you, even if it is a small matter, lower your requirements and make yourself as simple as possible. I believe you can be happy gradually.