Why we need religion?

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I have read this philosophy in one of the forum I've encounter. And it makes sense at all. Man feels pleasure and pain weather its physical, intellectual or emotional. Therefore a man lives his life to maximize his own pleasure and minimize his own pain. In many religion he is lead to believe that after his death he will either go to heaven (where in pleasures will be infinite) or hell (where in pain will be infinite). And in this religion he is also lead to believe that to get into heaven you must live your life on earth selflessly and that the self-interested go to hell. Thus, if all people believed these things, they would aim on earth to be selfless as possible and least self-interested and therefore became perfect, the world would be perfect. Thus this make sense to you? What do think why we need religion?