As far as I’m concerned, this is the greatest thing said about happiness by anyone ever:
This is the true joy in life, being used for a purpose recognized by yourself as a mighty one. Being a force of nature instead of a feverish, selfish little clod of ailments and grievances, complaining that the world will not devote itself to making you happy.
I am of the opinion that my life belongs to the whole community and as long as I live, it is my privilege to do for it what I can. I want to be thoroughly used up when I die, for the harder I work, the more I live.
I rejoice in life for its own sake. Life is no brief candle to me. It is a sort of splendid torch which I have got hold of for the moment and I want to make it burn as brightly as possible before handing it on to future generations.
George Bernard Shaw
I agree with the sentiments as long as I am over 90 by the time I’m all used up!
Not trying to take anything away from this sentiment, but what if the job you are doing serves no purpose to society? Even if you are good at it, and satisfied, even happy doing it, I would assume there is a breaking point.