The problem is not that you try, the problem is that you try too hard.
The fact about nature is that whenever you try to be cool so that you'll be accepted, it's usually difficult to achieve. Likewise trying to be happy, when you struggle to make yourself happy, you will end up not achieving that. I think the problem here is that you're trying too hard. I'll explain further.
Happiness like other emotions is not what you can just obtain, you have to live it, that is inhabited in it. For instance, when you are so irritated and pissed at something, at that moment you are totally not in control of your feeling in that state, you are unconscious of your state, and at that point you just do anything. Because you live in the anger.
A brave man doesn't get confused about his abilities to be brave, neither those a confident person gets to think in his heart or question if he is truly confident, because he lives in the reality of his being bold. It is the same case with happiness, a happy man doesn't see any reasons to feel otherwise, though situations will come, he doesn't let it still the reality that he is happy man.
Happiness doesn't just jump into anybody, it is a function of life experiences, it is definitely not achieved in itself, certain circumstances bring about happiness. It is funny these days how people sell happiness, happiness cannot be marketed or sold, you cannot buy happiness. It is just what it is. As soon as you get your life sorted out, putting your life in order, happiness brings to flow into you, you live happy, at this point, you won't have to force it. Positive achievement brings about happiness.
FACT: HAPPINESS is NOT synonymous to PLEASURE.
We all make this mistake of intertwining the concept of pleasure and happiness, well, I'm glad to tell you that pleasure is not synonymous to happiness, and by the pleasure I mean: partying, a new ride(car), losing 5 pounds, good food, seeing movies, plenty sex and so on. I'm not talking against the search for pleasure and all, but we should know that they are two different things and we should never co-related them. Although some form of pleasure brings about happiness, not all. For example, a drug addict is in the pursuit of his "happiness", but in the end, his health begins to pay the price. No to talk about adultery and how it has scattered families, that's a negative form of pleasure that never brought happiness.
A study has shown that people that spend their energy in materialistic and superficial pleasures don't always end well, they become emotionally deranged and unstable, less happy in the short run. It is, therefore, pleasure that is marketed to us, we fixate on it. No wonder they say that pleasure is an untrue god.
Pleasure is necessary but not sufficient. There is more to pleasure, most times we use it to distract ourselves and fill the space of our pursuit of happiness. Truth is happiness is long-lasting while pleasure is a short term feeling, it doesn't last.
When you try too hard to achieve happiness, you don't, you just need to be positive and do things that you enjoy, happiness will gradually creep in.