Just supposing there is a place/state of being called Heaven or Nirvana or whatever you want to call it. An afterlife in which the unhappy people of this world will be made happy and the evil bastards will be made to pay (presumably with some kind of unhappiness, like death for instance). OK. So far so good. But if I believe that in the afterlife my unhappiness will be replaced with happiness then that would make me happy now wouldn't it? So I would no longer be unhappy. What does that leave for the proposed afterlife? I guess all I have to do is believe I'm going to be happy, then I will be happy.
Just a bit of blue-sky thinking I thought I'd float past you and see if anyone saluted it or tore down the flagpole. Not that I'd want to die in a ditch over it, clear blue water or not.