On one hand you have to master the Game of Life, and know how to play the best the hand you were served.
You have to learn all the necessary skills that you require in life, like knowing how to manage your relationships, earn your existence or protect yourself.
And based on how well you will perform at this will have a certain degree of influence over your happiness. Because the body gives you feedback in an attempt to help you take the best decision as possible. For example when you are making a lot of money you'll feel happy and when you're not making so much you feel sad or disappointed.
Unfortunately it is impossible to avoid this fluctuations in life, there will always be times where you do better or worse. So your happiness will always fluctuate, to more exactly answer the question are you happy you need to know at what point in your life.
So then we have the interesting phenomena of Fairly successful people being chronically unhappy. Regardless that achieved, many enviable accomplishments and from the outside everything looks perfect, sometimes these people are quite miserable. Think of all the examples of famous people that either had problems with addiction or committed suicide.
This is a problem, if being unhappy for a short period of time is unavoidable, being chronically unhappy is problematic or we could consider it a disease.
There are two reasons why you could be unhappy:
Happiness requires a certain intensity of effort, for the most part we live in an environment where we didn't have all the modern convenience and labor saving devices that we have today. So we developed an insurance called happiness that assures us that we are more likely to do the work when there is some pleasure in the process of working towards pleasure.
If there is a solution to this it has to be finding out the truth, as mental health is having an accurate model of reality inside your mind. This can only be established through the self discipline of always finding the truth. I don't mean like control your thoughts or emotions, because over this you have very little control, if you could control your emotion you would already feel happy all the time. Attempting to control things over which you have no control you are rather suppressing your emotions, which on a long term it will lead only temporary periods over which you feel under control followed by aggressive outbursts and relapse.
The truth sets you free, not free of your emotions like your pain free from sufferance the chronic pain. Like the classic Greek philosophers argued to know is to do. When you truly know something it is impossible to don't practice it as well.
