think it's why atheists are so passionate about their disbeliefs. They're envious of a religious person's happiness being religious. If you don't believe in even the possibilities, i'd be unhappy and militant too.
if that was the case, christianity and other major religions would not be on the rapid decline. It is the social aspect of religion that is uplifting and fulfilling and makes people happier not the religion itself.
"there are a number of mechanisms through which religion may make a person happier, including social contact and support that result from religious pursuits, the mental activity that comes with optimism and volunteering, learned coping strategies that enhance one's ability to deal with stress, and psychological factors such as "reason for being." (studies on religion and happiness (wikipedia)).
Atheists value reason over superstition; they are passionate about reality. They do not pretend to believe in an afterlife or hope for an afterlife and, for that reason, are purpose driven in the one life of which they are certain...this one!