“If you want to lift yourself up, lift up someone else.”

Junkie (1953)

"Chicory and Daisies"
Al Que Quiere! (1917)

Charging Barack Obama with plagiarism at Texas presidential debate, February 21, 2008 http://www.time.com/time/quotes/0,26174,1715473,00.html; see relevant quote above, two days earlier
Presidential campaign (January 20, 2007 – 2008)

Wessex Poems and Other Verses (1918)

Source: Traveling Light: Releasing the Burdens You Were Never Intended to Bear

Actually a statement by William J. H. Boetcker known as "The Ten Cannots" (1916), this has often been misattributed to Lincoln since 1942 when a leaflet containing quotes by both men was published.
Misattributed
Context: You cannot bring about prosperity by discouraging thrift. You cannot strengthen the weak by weakening the strong. You cannot help small men by tearing down big men. You cannot help the poor by destroying the rich. You cannot lift the wage earner by pulling down the wage payer. You cannot keep out of trouble by spending more than your income. You cannot further the brotherhood of man by inciting class hatreds. You cannot establish security on borrowed money. You cannot build character and courage by taking away a man's initiative and independence. You cannot help men permanently by doing for them what they could and should do for themselves.

Variant of this quote "The best way to cheer yourself is to cheer somebody else up." is misattributed to Albert Einstein.
Source: According Quote Investigator Mark Twain did write a version of this saying in a personal notebook in 1896, and it was published by 1935 in “Mark Twain’s Notebook”. https://quoteinvestigator.com/2012/12/21/cheer-somebody/

Source: Rose Under Fire