Unhappiness is the incapacity to understand life, the incapacity to understand oneself, the incapacity to create a harmony between you and the existence.
Unhappiness is a discord between you and reality; something is in conflict between you and existence.
Happiness is when nothing is in conflict when you are together, and you are together with existence also.
When there is a harmony, when everything is flowing without any conflict, smooth, relaxed, then you are happy.
Happiness is possible only with great understanding, an understanding like the peaks of the Himalayas. Less than that wont do.
Himanshu Kumar Singh.
Keep Smiling & Take Care.