My greatest enemy?

(J. C. Philpot, "Israel's Happiness" 1859)

I have ever found myself to be my greatest
enemy. I never had a foe that troubled me so
much as my own heart; nor has any one ever
wrought me half the mischief or given me half
the plague that I have felt and known within.
And it is a daily sense of this which makes me
dread myself more than anybody that walks
upon the face of the earth!

Keep a watchful eye upon every inward foe;
and if you fight, fight against the enemy that
lurks and works in your own breast!