“Selfishness comes from too little self-love, not too much, as we compensate for our lack. There’s no such thing as caring for the self too much, just as there’s no such thing as too much genuine affection for others. Our world suffers from too little self-love and too much judgment, insecurity, fear, and mistrust. If we all cared about ourselves more, most of these ills would disappear.”

Chap. III.
The Theory of Moral Sentiments (1759), Part III
Context: When the happiness or misery of others depends in any respect upon our conduct, we dare not, as self–love might suggest to us, prefer the interest of one to that of many. The man within immediately calls to us, that we value ourselves too much and other people too little, and that, by doing so, we render ourselves the proper object of the contempt and indignation of our brethren. Neither is this sentiment confined to men of extraordinary magnanimity and virtue. It is deeply impressed upon every tolerably good soldier, who feels that he would become the scorn of his companions, if he could be supposed capable of shrinking from danger, or of hesitating, either to expose or to throw away his life, when the good of the service required it.

The Dangers of Feeling Like a Fake, 2005

Source: The Captain is Out to Lunch and the Sailors Have Taken Over the Ship

Inaugural address (4 March 1921).
1920s

Source: A Book of Simple Living

Source: The Duke's Children (1879), Ch. 66

The Golden Violet - The Rose
The Golden Violet (1827)

Disputed
Source: Claimed to be from Men Without Women, but it does not appear in that work. May have originated in a 2011 blogpost by Marc Chernoff entitled 30 things to stop doing to yourself http://www.marcandangel.com/2011/12/11/30-things-to-stop-doing-to-yourself/.

Source: Gone with the Wind