I watched The Avengers (2012).
In the movie's last battle, when the big alien ship comes near the Hulk (Bruce Banner), the Hulk talks with a friend (like Iron Man, Captain America etc..).
In that scene the Hulk says he is always in angry.
What is the reason behind him being always angry?
In the beginning of the Avengers movie, Black Widow finds Banner in India, treating sick children. This isn't just a humanitarian endeavor for him; Banner purposefully surrounds himself with injustice - with poverty, with senseless death - so that he could be constantly angry at something.
Being constantly angry allows him to keep his anger under control - it's not a sudden spike of anger that disrupts his concentration and lets the Hulk out, it's a constant, background anger that lets him decide when to unleash the green beast.
From the script:
NATASHA
You know, for a man who's supposed to be
avoiding stress, you picked a hell of a place
to settle.
BANNER
Avoiding stress isn't the secret.
This doesn't say it explicitly, but implies to me that his choice of location and activity are part of his secret.
He just is a angry person. Some people are prone to rage. Unfortunately, Bruce Banner's rage comes with disastrous consequences, so he is forced to control it. Mostly via meditation and breathing exercises, otherwise anything could send him over the edge on a rampage. He has plenty of reasons to be angry as well. He hurt his GF on the first transformation, he was hunted by his GF's father, that had previously lied to him and put him in this situation in the first place.
The upside, is that when he needs to transform, he just stops controlling it, and he can simply transform.
The attitude he describes is one more associated with Eastern thinking. If I had to venture a guess, I'd say it's closest to Zen thinking:
A man traveling across a field encountered a tiger. He fled, the tiger after him. Coming to a precipice, he caught hold of the root of a wild vine and swung himself down over the edge. The tiger sniffed at him from above. Trembling, the man looked down to where, far below, another tiger was waiting to eat him. Only the vine sustained him.
Two mice, one white and one black, little by little started to gnaw away the vine. The man saw a luscious strawberry near him. Grasping the vine with one hand, he plucked the strawberry with the other. How sweet it tasted!
Zen parables often can have many meanings, but one I would point out is that, if the man were to fret about his situation, it would eat him up inside. In the case of this man, it would prevent him from enjoying the last strawberry. In the case of the Hulk, having an anger (about losing control to anger) eating him up inside would have more disastrous consequences.
This is the lesson for negative emotions. Negative emotions breed more negative emotions. If you are the Hulk, and negative emotions are really really bad, the only way to be free is to embrace them, smile at them, and from time to time, smash some things.
