The key to happiness I learned from martial arts is one word, and that is to coexist.
In order to coexist we need to look for similarities rather than differences.
Most people look at differences and it creates a negative effect.
The ability to look at differences and turn it into something positive is a higher skill so don't do it unless you have this ability.
Differences divide us, separation into groups cause fear, ultimately this turn into conflict, whether it's verbal, physical, or both.
In other words differences causes fighting, combat, and war.
The combat method solves problems by beating the other force and then the winner gets to impose their will without any concern for the other force or their view points.
This method only creates resentment and it's the most primitive way to do things.
It is the stupidest way to solve problems.
Remember to always look for similarities.
It could be the smallest thing in life, for example when a salesman rings your doorbell.
First make sure that you don't open your door.
You never know who the other person is and it can leave you vulnerable to very bad situations.
Anyway some guys get really mad, I mean really angry and upset, I will kill this bastard for trying to sell me something I don't want or need!
If you look at differences your going to think like, I would never get a job like that, what kind of person would take this job, get a real job! This person would sell their own mother and grandmother!
Instead look at similarities, this person is human and just trying to make a living, we both live in a tough world where money is needed.
When you look at similarities it will calm you down a little. Keep thinking that way and it will take away your anger. And the more you do this, the more pleasant you will become, and you will start to notice that the human interaction you have in your life is getting better.
Remember coexisting equals happiness.
The opposite of coexisting is war which is misery.