Horace Mann Quote
Doing nothing for others is the undoing of ourselves. We must purposely be kind and generous, or we miss the best part of existence. The heart which goes out of itself gets large and full. This is the great secret of the inner life. We do ourselves the most good doing something for others.
Quoted in Thoughts (1901) by Jessie K. Freeman and Sarah S. B. Yule, p. 83, and in Collect Writings of Russell H. Conwell (1925), Vol. 1, p. 396