If I run with this then I have to accept the premise that the majority of people are more interested in making other people unhappy rather than making themselves happy. My first inclination is to say bollox to that as I would presume most people are basically selfish and would therefore naturally care about their own happiness above anything else.

On the other hand, maybe the quote is possibly trying to give a deeper insight by suggesting that most people are incapable of finding happiness or of being happy or satisified and consequently end up trying to ruin everyone else's happiness in retaliation for same. If I accept that premise, then maybe it's not a bad quote after all.

Then again, maybe I'm over analysing this way too much! :-)