Sonny Lykos referenced me to an online version of this article (not from this source) quoting a 1940 speech by Albert A.N. Gray presumably to a group of life insurance salespeople. It is a timeless classic.
“The common denominator of success --- the secret of success of every man who has ever been successful --- lies in the fact that he formed the habit of doing things that failures don't like to do.”
Here is a link to the complete article:
Lykos referenced a source, a marketing consultant using free (non-copyrighted) web materials, and an ill-maintained blog to develop search engine traffic. I can't vouch for the actual reference source here (apparently a young student), but it seems much more genuine to me.