“One who gains strength by overcoming obstacles possesses the only strength which can overcome adversity.”

Quotes, Concession speech (2000)
Context: I know that many of my supporters are disappointed. I am too. But our disappointment must be overcome by our love of country.
And I say to our fellow members of the world community, let no one see this contest as a sign of American weakness. The strength of American democracy is shown most clearly through the difficulties it can overcome.

David Webb Show http://www.breitbart.com/big-government/2015/08/05/ohio-male-rnc-member-calls-carly-fiorina-hot-babe/ (5 August 2015).
2010s, 2015, David Webb Show (August 2015)

Majlisi, Bihārul Anwār, vol.75, p. 165

Oromis
Eldest (2005)

Source: Aphorisms and Reflections (1901), p. 164

Napoleon : In His Own Words (1916)

It – How Churches and Leaders Can Get It and Keep It (2008, Zondervan)

Interviewed by Harry Kreisler, February 28, 2003. In Conversations with History http://globetrotter.berkeley.edu/people3/Dalgarno/dalgarno-con0.html. Institute of International Studies, UC Berkeley.
Context: Research is a matter of overcoming obstacles. That's what research is about. There are problems. There are difficulties. It's hard to make sense of a collection of information or whatever. Obstacles are the nature of research. Maybe that's why some people give up. There's always an obstacle. You overcome one to find there's another one.