From the day we are born we are destined to be unhappy to some extent.  If as newborns we are not fed, clothed and sheltered we are miserable and we can only cry.  We have not yet developed the ability to say "I'm thirsty" or "I'm tired, leave me alone".  Over time we learn to speak, to eat, to share our toys, to dress ourselves, to work, to find and maintain lasting friendships and to reach out and help others achieve higher levels of being.  But at each step of the way there is a learning curve that can be painful to the spirit, if not the body.

Unhappiness has many roots.  Not having what we want is a big source.  The prayer, "God give me the courage to change the things I can, the serenity to accept the things I can't, and the wisdom to know the difference" lies close to the heart of the issue of how to deal with unhappiness.  The question on the level of the individual is perhaps better phrased as how to change things that should be changed (if I hate someone and I own a gun, I am physically able to but should not go kill that person), how to accept the things that can't be changed, and how to know the difference.

So minimizing unhappiness involves directing and focusing our energy as well as we can so that we provide ourselves with as much as our technology allows so there is enough of everything to go around.  This levels the playing field in terms of materialistic "haves" and "have-nots".  (This does not mean that anything anyone wants is theirs for free.  It means that there is more of what people want because they have said what they wanted and realigned production to create more.)
It also involves teaching people from an early age how to cultivate and keep good friends.
People also need some sort of thing that they can do well, of which they can be proud - like a job or hobby - that gives them a way to feel they deserve the respect of their peers.
And it requires "active karma" - as people learn to put their trust in and do more good for others, they will find their own environment less and less likely to have hostile intrusions.
 

[To some extent our mother tongue actually shapes how we think - different languages have varying numbers of words to talk about something.  People who live high in the mountains or far north will have many words for types snow and few for ocean tides.  Where the nouns, adjectives and verbs fall in a sentence may influence us.  English is a very "do" oriented language - English teachers often counsel students not to use the passive voice.  Not so for Spanish.  Our environment determines what we think and feel.]