Failure type personalities look for excuses for their failure and they will often blame society, "the system" or life. He resents success and happiness of others because it is "proof" that life is treating him unfairly. Resentment is a way to protect ourselves and make our failure palatable by explaining it in terms of injustice.
Resentment is a poison to the spirit and makes happiness impossible. It uses up all of your power that could have been pushed forward towards accomplishment. It turns everything into a vicious cycle.
This resentful person has a chip on their shoulder and is not a good companion for colleagues. Any attempt to point of deficiencies is met with additional feelings of resentment.
Resentment provides a way to feel important. There is a perverse sense of satisfaction from feeling "wronged". There is a feeling of moral superiority and the need to "prove your case" before the court of life. There is no magic that will reward him for negative feelings.
Resentment is an emotional rehashing of an event from the past. You cannot win when you try to do the impossible - change the past. It becomes an emotional habit and you start to picture yourself as a victimized person. You carry around the feeling and you seek out injustices against you. They feel good when they feel miserable because it has become their habitual state. Resentment habits go hand in hand with the inferior self-image. You begin to imagine yourself as a pitiful person who deserves to be unhappy.
Resentment is caused by your own reaction and you have the power over it by convincing yourself that self-pity is not ways to happiness. If you harbor resentment you cannot picture yourself as a self-reliant, independent person who is the "master of his fate". You are not owed eternal gratitude and undying appreciation so you feel resentful when debts are not paid. Resentment is incompatible with creative goal-striving where you are not passive but you are an active participant. You set your goals and nobody owes you anything.
You are responsible for your own success and happiness. Resentment has no place in the picture of your life and that is why it is part of the Failure Mechanism. Source - Psycho-Cybernetics by Dr. Maxwell Maltz