Happiness is a mental state. Usually our moods are derived from the higher cortex in our brain.
How do you get mental satisfaction?
I doubt you can buy it since it's a mood.
Unless you buy mood- altering drugs.
There are some people who are born happy.
But I think it is a natural brain process a is sadness or anger.
There are transmitters which excite the brain which makes one happy.
They have done MRI's of people who are happy and those who are depressed.
I've seen them and there is a vast difference between the two.
A happier brain has more yellow in it compared to a person who is depressed. A depressed persons brain shows little or no color meaning less transmitters which keep the brain communicating with other parts of the brain.