'Shall Satan keep a crafty watch, and shall Christians not keep a holy spiritual watch? Our whole life is beset with temptations. Satan watches all opportunities to break our peace, to wound our consciences, to lessen our comforts, to impair our graces, to slur our evidences, and to damp our assurances. Oh! what need then have we to be always upon out watch-tower, lest we be surprised by this subtle serpent. Watchfulness includes a waking, a rousing up of the soul. It is a continual, careful observing of our hearts and ways, in all the turnings of our lives, that we still keep close to God and his Word.
Watchfulness is nothing else but the soul running up and down, to and fro, busy everywhere; it is the heart busied and employed with diligent observation of what comes from within us, and what comes from without us and into us. Ah souls! you are no longer safe and secure than when you are upon your watch.'
Thomas Brooks, Precious Remedies Against Satan's Devices, p.247.