It must never be forgotten that the flesh is weak and naturally inclined to slumber. We need a constant renewal of the divine impulse which first started us in the way of service. We are not as arrows, which find their way to the target by the sole agency of the force with which they started from the bow; nor as bird, which bear within themselves their own motive power: we must be borne onward, like ships at sea, by the constant power of the heavenly wind, or we shall make no headway. Preachers sent from God are not musical boxes which, being once wound up, will play through their set tunes, but they are trumpets which are utterly mute until the living breath causes them to give forth a certain sound. We read of some who are dumb dogs, given to slumber, and such would be the character of us all if the grace of God did not prevent. We have need to watch against a careless, indifferent spirit, and if we do not is we shall soon be as lukewarm as Laodicea itself.

–C.H. Spurgeon, “Earnestness: Its Marring and Maintenance,” Lectures to My Students.