It is a most fearful fact to think of, that in every heart there is some secret spring that would be weak at the touch of temptation, and that is liable to be assailed. Fearful, and yet salutary to think of; for the thought may serve to keep our moral nature braced. It warns us that we can never stand at ease, or lie down in this field of life, without sentinels of watchfulness and campfires of prayer.

Living Words (ed. 1860)