“Folks are usually about as happy as they make their minds up to be.”
Often misquoted as: "I have found that most people are about as happy as they make up their minds to be." or "People are just as happy as they make up their minds to be."
This quote is not found in the various Lincoln sources which can be searched online (e.g. Gutenberg). Niether does Lincoln appear more generally to use the phrase "making up {one's} mind". The saying was first quoted, ascribed to Lincoln but with no source given, in 1914 by Frank Crane and several times subsequently by him in altered versions. It was later quoted in How to Get What You Want (1917) by Orison Swett Marden (Thomas Y. Crowell Company, 1917), 74, again without source. Alternative versions quoted are: "I have found that most people are about as happy as they make up their minds to be" and "People are just as happy as they make up their minds to be."
Zdroj: https://quoteinvestigator.com/2012/10/20/happy-minds/#:~:text=%E2%80%9CPeople%20are%20about%20as%20happy,up%20their%20minds%20to%20be.%E2%80%9D&text=Remember%20Lincoln's%20saying%20that%20%E2%80%9Cfolks,up%20their%20minds%20to%20be.%E2%80%9D
Curiously in later books Crane, e.g. Four Minute Essays, 1919, Adventures in Common Sense, 1920, "21", 1930, Crane mentions other routes to happiness and does not again use this quote.
Marden used a great many quotes in his writings, without giving sources. Whilst sources for many of the quotes can be found, this is not true for all. For instance he mentions another story in which Lincoln says "Madam, you have not a peg to hang your case on"; this also does not seem to found in Lincoln sources.