Happiness is the experiences of pleasure and purpose over time. It is pleasant, because we love fun. It is purposeful, because we crave for achievement. It is the feelings we experience, not the measurements others impose. It is an authentic documentary recorded over time, not a contrived snapshot taken at one point.
As every life has a span, pursuing happiness means how to allocate limited time between purpose and pleasure, and live with the consequences of those choices, here and now.
In technical terms,
where is the happiness function in the two dimensional space of purpose and pleasure, is the actions we take at time t, is the environment.
[Vancouver, Nov., 2013]