Oh my @scienceblocks what a wonderful comment this is. Filled with honest, non-judgmental self-reflection. This is truly the right road towards personal growth :)

I have always held the grudge. And I have not forgotten a single one of those incidences.

Oftentimes this happens because of individuals' cognitive style. Those who tend to present this mode of thinking are understood to be ruminators ^ref.

Does any animal show prolonged grudge? Like does anger have a role to play beyond fight part of fight or flight response in them?

These are interesting questions indeed :) And, I have written them down to look into them later on, when I have some free time. It may answer many of my own queries. But, the thought of non-human animals holding a persistent ill-feeling towards something that happened a long time ago, is a difficult one to fathom.

The most frequent kind of rage I display is related to someone trying to push me out of my comfort zone. Not entitlement.

Here, it would be interesting if you could identify the thoughts that go through your head when this happens. Through pinpointing them you may unveil what is that makes you angry. Do they feature any cognitive distortion? For example: (1)inaccurate assumptions of what the other person is thinking, (2)jumping to conclusions about the other person's intentions, and so forth.

That would explain the psychology behind it (the cognitive style). As for the biology, all the neurobiological mechanisms underlying rumination (or repetitive thinking for that matter). Rumination has been found to correlate, for example, with activity in the ventromedial prefrontal cortex, anterior cingulate cortex, anterior insula, and posterior cingulate cortex ^ref.

Your comment is very kind and encouraging @scienceblocks. It makes all the time and energy I put into my work here on the platform worthwhile. I feel very grateful for all those of you who read my writings. It means the world to me.

Thank you so much for taking the time to let me know that, somehow, this post has had a positive impact on you. Thank you :)

All the best to you. Always and forever!
Abigail.