The cultural obsession with happiness can contribute to unhappiness. We are programmed to believe that if we are not happy there is something wrong with us. What happens is that we begin to feel bad and then subconsciously we feel bad that we feel bad because feeling bad is wrong.
We need to understand that it is ok to be sad, it is ok to be angry and it is ok to be disappointed. We need to feel our emotions if we are to be happy. We need to give our "negative" emotions a chance to exist. If we sit on our sadness it festers, and rots at the happy moments.
Giving ourselves over to the moment and the emotions that live in the now is the best way to see ourselves through. If we do not we carry the baggage and the hurt with us for our entire lives.