personally, I think there is a certain "groaning" or pain that we all endure right from birth. Even if you supposedly feel like a million dollars, eat healthy, feel healthy, I think there is a certain pain or constraint we endure. Ive been coming to realize that the feeling of pleasure is in close range with pain ( eg. sexual climax, or like the sensation after a stomach ache passes). So this pain that we feel all the time has been intertwined in our pleasure.

I dont know how to explain it, but I think its the weight of our physical body chaining and breaking down constantly during our life. The containment of our mind in a physical form (the brain) hurts it and prevents it from freedom. So ultimatly, I think that right after death, you feel a freedom and rest like youve never felt before. Rest of mind, body and soul. Personally, I think that even the most evil of mankind get an intitial rest after dying.

And after that rest, well no one knows.... except forum posters