Except not everyone has the same type of happiness. This is why the declaration of independence does not say "life, liberty, and happiness", it says "life, liberty, and _the_ _pursuit_ _of_ happiness". There's an implied statement there that not everyone, or even most will be happy, but we should be free to be able to seek what makes us happy. You don't have a right to happiness, but you have a right to be able to try to make yourself happy.