When people are motivated by guilt, shame, jealousy, possession, etc. It is usually a result of trauma, and their actions that follow can be quite hurtful to others. Here is where I rationalize the root of resentment. Even though you are entitled to feel pain, you also have to work to understand the motives in play. To comprehend the pain body of self and others, the lessening you will skew toward the simplification of resentment.
Furthermore, you are only hurting yourself. The toxicity seeps through your system like the Psychomagnotheric Slime in Ghostbusters II. It holds you back and unnecessarily keeps negative energy pinned on others. I have found it comes from the shock of others' actions, wondering why that was their choice until I dig deeper. As much as we can try to not take things personally, there are always going to be those variables.
When I view resentment in my thoughts and feelings, I go back to negative examples witnessed in different dynamics. This grounds me in my arrogance toward feeling even the slightest dependency of the toxic ooze. I've learned the difference is sitting in those feelings to determine why they hurt you so deeply in the first place and you have to do this to release their power over you. See, resentment is simply stagnant energy used as a crutch to not like someone or something. Maybe it reminded you of a deeper suppressed wound or it straight up embarrassed you. Maybe that is how the other party felt too as they acted out whatever they did that hurt you.
Resentment is a nasty destroyer of happiness. It permeates into other experiences without warning and you, and if you're not going to become a supervillain, it's pointless to hold onto. Every moment of pain or trauma in your life holds an opportunity for you to learn, grow, and find more compassion. It's also totally okay to not like someone. Perhaps part of the resentment you feel reflects your lowering your standards or acting out of your insecurities. It might ultimately not be because of their actions toward you. I have found that most people I could hold resentment toward only were operating out of their pain. So though I had to take time to heal and release negativity toward them, I entirely knew where their actions were derived from. It's never an excuse, to clarify, but it is also in your acceptance to see it as a way you would not act. Instead of holding resentment take it as a lesson to stay in your integrity.
Resentment makes you reactive, which is irrational. These comprehensions I mention are reflective post-experiences that could have triggered this easy choice within me, so the intention is to explain the realizations to nip things in the bud instead of perpetuating them. You can't rationally remain upset with past scenarios if they prompted you into growth. The choice for me to release any tendencies of resentment came from the ill-fated examples I had. It has been identifying the opportunity to find a balance between personal boundaries and keeping an open heart. To also still find rage about things is not (to me) reflective of resentment. It just means that you are working through those emotions. The particular instance is simply a conceptualized understanding for you to hold as an example, not still holding attachment to the people, places, and things from where you previously sought pain. Let them be stories to educate you on where you still have room to grow. Remember things are not done to you, they are done for you. The perpetrator has his or her story to tell. Stop allowing them access to yours.