“We are actually in the middle of a battle, fighting the devil who is none other than ourselves.”

1910s, The New Nationalism (1910)

Anastacia: Speaks frankly about her new body, finding love again and using her voice to inspire other http://www.anastacia.com/hello-magazine/, Hello Magazine, April 14, 2014.
General Quotes

Variant: Such a simple concept, yet so true: that which we manifest is before us; we are the creators of our own destiny. Be it through intention or ignorance, our successes and our failures have been brought on by none other than ourselves.
Source: The Art of Racing in the Rain

This quote is widely attributed to Margaret Thatcher on various websites, and also appears in a number of books, including The Concise Columbia Dictionary of Quotations, Columbia University Press (1989), ed. Robert Andrews, p. 320 : ISBN 0231069901. 9780231069908 , but without any further source information such as date, location or any other context.
One valid Thatcher quote which may be the basis for the version above appears in the Second Carlton Lecture http://www.margaretthatcher.org/document/105799 (‘Why Democracy Will Last’), delivered at the Carlton Club, London (November 26, 1984) : Mr. Chairman, each generation has to stand up for democracy. It can’t take anything for granted and may have to fight fundamental battles anew. You know that marvellous quotation from Goethe : ‘That which thy fathers bequeathed thee / Earn it anew if thou would possess it.’
Thatcher also expressed this thought in a Speech to Atlantic Bridge (May 14, 2003) http://www.margaretthatcher.org/document/111266, delivered at the St. Regis Hotel, New York City : My friends, every generation has to fight anew the battle for liberty.
Disputed

The Art of Poetry on a New Plan (1761), vol. ii. p. 147.
The saying "he who fights and runs away may live to fight another day" dates at least as far back as Menander (ca. 341–290 B.C.), Gnomai Monostichoi, aphorism #45: ἀνήρ ὁ ϕɛύγων καὶ ράλίν μαχήɛṯαί (a man who flees will fight again). The Attic Nights (book 17, ch. 21) of Aulus Gellius (ca. 125–180 A.D.) indicates it was already widespread in the second century: "...the orator Demosthenes sought safety in flight from the battlefield, and when he was bitterly taunted with his flight, he jestingly replied in the well-known verse: The man who runs away will fight again".

1983 Progressive Conservative Leadership Convention speech, June 10, 1983.

Remarks by el-Sisi during a military conference (28 April 2013) http://www.youtube.com/watch?v=LC93fn9s3-c.
2013
Variant: Simply, all what we did is that we avoided the country a big crisis and a battle between Egyptians. Beware, instead of Egyptians fighting each other, no, you can fight us, and we protect all. how many would fight us? but Egyptians fighting each other would be a big war we couldn't have had the ability to deal with.

" Blair launches stinging attack on 'absurd' British Islamists http://observer.guardian.co.uk/politics/story/0,,2115929,00.html", 1 July 2007.
Remarks made on the eve of his departure from Downing Street, 26 June 2007.
2000s