Pleasure and Pain

What do we know about pleasure and pain. Perhaps not the best question to answer especially after 14 hours of work. But really what do we know about pleasure and pain. I am not looking for some obvious answers. Obviously they are two extremes of human emotion and we keep switching ourselves from one nook to another. While both leads us to a level of deep emotional understanding and synchronization of energy, they differ in the content. By content I mean to say the content that takes us to an emotional equilibrium. While both of them sound contrasting to each other, a positivity keeps lashing out of each. May be the heart is made to think and mind is meant to reason and they together are meant to endure pain and pleasure.

So the question still remains - What do we know about pleasure and pain