Life is all about choices, happiness happens to be one of them. Happiness depends on perspective. Some are happy for what they do have, some are upset for what they don't have. Happiness isn't decided by one factor, it’s everything in life coming together for one common goal.
Happiness is not the absence of problems, its the ability to deal with them. Everyone has run into some type of problem, it matters about how you deal with it. Being unable to deal with what life throws at you could be a problem.