Where can you find poem first line is This is the true joy in life by george bernard shaw?

http://www.brendanmcphillips.com/the-true-joy-in-life-by-george-bernard-sThe True Joy in Life by George Bernard Shawby Brendan McPhillips

George Bernard Shaw wrote the following sentence in a letter prefacing his book "Man and Superman: a Comedy and Philosophy" which can be used as a guide to living a meaningful, productive and joyful life: This is the true joy in life, the being used for a purpose recognized by yourself as a mighty one; the being thoroughly worn out before you are thrown on the scrap heap; the 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.

George Bernard Shaw

Epistle Dedicatory to Arthur Bingham Walkley

"Man and Superman: a Comedy and a Philosophy"

The following is an elaboration on the four points that George Bernard Shaw makes to finding the true joy in life: