Peter had used this verb be sober-minded
twice before in this letter (1 Peter 1:13; 1 Peter 4:7). The term contrasts with being drunk (see Genesis 9:24). The point of the imperative is that Peter wants his readers to be clear-headed. Seeing suffering through the lens of self-pity clouds one’s assessment of what is happening and hence how one ought to respond. Any such confusing lens must be removed. God’s “mighty hand” will always direct events to his people’s benefit.
8 Be sober-minded; be watchful. Your adversary the devil prowls around like a roaring lion, seeking someone to devour.