Resentment is a complex, multilayered emotion that has been described as a mixture of disappointment, disgust, anger, and fear. Other psychologists consider it a mood or as a secondary emotion that can be elicited in the face of insult and/or injury. Wikipedia
Resentment has for me, become apart of my awareness after the resentment has passed. Like some people feel when they become angry. They have no immediate control of the anger until the situation has passed. When I was young I used to have resentment towards my friends going to camping trips or to the movies. As I got older I realized my mother was not able to provide the means for me to go on camping trips or buy the toy I so wanted. This resulted in my reduction of resentment and gained understanding of the inequality that life has.
This has been a somewhat positive aspect in my adulthood. At times I'm not phased when friends go to concerts without me or have fancy cars. There are times it feels like I would want these things but not that I feel resentful of these items and experiences. It would be nice to have a new car. It's cool that my friend has this new car. However, there is a negative that sometimes makes way. My immediate distaste in wasteful purchases. The judgement that is twofold in retrospect to my own choices.
Resentful Reaction. The thought process of understanding another persons views and actions based on current and past traumas. No matter the suffrage there is always trauma and no matter the trauma there is always a Resentful Reaction. However, this reaction to feeling resentful diminishes as life experience builds up. The more knowledge an individual has of this life the less resentful they will become.