It's also very new. I never thought like it. I'd say lif is bliss but not pain. However your definition of pain makes sense. 

IamSINGLE

Haha! I'm not a miserable person  I swear! I just think pain is a very defining part of life, and especially the human existence. 

Aardvark

plebpoet

AskSN

What is LIFE in one word?

Pain. 

We all suffer to lesser or greater degrees. I think how we manage that, and what lessons we learn from it is what makes us who we are. 

I'd go so far as to argue that it's a large component in what drives evolution. 