To me sadness is a perpetual default medium of our lives. People emerge themselves in the posession/accomplishment paradigm as to form a denial bubble for themselves. This bubble gives the people meaning for their life, even though this meaning may be artificial and constructed by self gratification or fear of emotional/physical pain.
My cousin has a house, a beautiful wife, two children and is surrounded by many trusted friends. Yet him and his wife consistently ask everyone around them "What is the meaning of life". He first thought it was children, but then he admitted that they are not always the answer, nor is money or sex. So at the end it comes down to that empty feeling of going nowhere, only to be succeded by a surge of endorphins at a mere hint of pleasure, only to crash down again and repeat the vicious cycle. Its 1 am on a cold midfall night and I think I am getting carried away