'Holding in' your anger makes you a better person than doing something to 'release' it:
The people in both groups were told they were going to have to compete against the person who graded their essay. One group first had to punch a bag, and the other group had to sit and wait for two minutes.
After the punching and waiting, the competition began.
The game was simple, press a button as fast as you can. If you lose, you get blasted with a horrible noise. When you win, blast your opponent. They could set the volume the other person had to endure, a setting between zero and 10 with 10 being 105 decibels.
Can you predict what they discovered?
On average, the punching bag group set the volume as high as 8.5. The timeout group set it to 2.47.
The people who got angry didn't release their anger on the punching bag, it was sustained by it. The group which cooled off lost their desire for vengeance.
In subsequent studies where the subjects chose how much hot sauce the other person had to eat, the punching bag group piled it on. The cooled off group did not.
Your habits have a large effect on your mental states. If you act angry more often, you will become an angry person. If you act peaceful more often, you will become a more peaceful person.