We don't know, and we never will know. You can either live with that truth, or paste over it with myths, as man has done since the dawn of time. Those who cannot live with the unknown have convinced themselves that we go to ethereal lands of pain or pleasure based upon our beliefs and actions. Those who however accept that we will never know commonly believe that we simply stop existing, which would neither be pain nor pleasure nor anything at all. The only perceived undesirability of this non-existence is the thought of not going to some sort of world designed purely for your eternal pleasure, a concept which in all honesty is probably equally non-existent.