Several words are used in Scripture to imply spiritual watchfulness, and each has a slightly different meaning. Only as we compare and combine these words do we get the full force of the Scripture exhortations to watchfulness.
One such word is the Greek word agrupneo, translated "watch." In Mark 13:33 we read, "Take ye heed, watch and pray: for ye know not when the time is." The word literally means to be sleepless and comes from two Greek words meaning "to chase" and "sleep." It implies a purposeful and active state of awareness.
More commonly used is gregoreo. It is a stronger word, meaning to arouse oneself and shake off lethargy, implying activity as on the part of one who is fully awake. "Watch ye, stand fast in the faith" (1 Corinthians 16:13), and "continue in prayer, and watch in the same with thanksgiving" (Colossians 4:2). "Watch ye, therefore: for ye know not when the master of the house cometh" (Mark 13:35).
A third word is nepho, which literally means to abstain from drink which would produce stupor, as well as sleep, and therefore conveys the additional idea of sobriety. By combining the teaching of these three words, we are instructed not only to keep awake but to keep active and to avoid the intoxication of this world's seductive pleasures.
In our text, we see that we are not only to be sober (nepho) and vigilant (gregoreo), but we also see the reason why. Our "adversary the devil" is a vicious opponent. He stalks us both day and night with brutal cunning. We dare not underestimate him by figuratively closing our eyes in sleep or dulling our senses with intoxicants. "Wherefore gird up the loins of your mind, be sober" (1 Peter 1:13). JDM http://www.icr.org/articles/type/6/