This verse indicates that there is little room for carelessness. We are being called upon to be thoroughly self-controlled and to be alert. Why? Because Satan aims to undermine our confidence, to sow discord, and to get us to stop believing and revert to carnality. These are the directions in which he will try to push us.
Notice Peter writes, "Whom he may devour." "May" indicates permission is given. He has the ability to devour us spiritually, but it does not have to happen. Putting the advice in verse 8 into more common language, instead of saying. "Be sober," we might say, "Keep cool," "Keep your head screwed on right," "Don't lose your presence of mind," "Try to keep calm about this," "Don't be fearful," or "Don't lose your temper."
He also says to "Be vigilant," which means "to watch." This same phraseology is used in reference to prayer. It is part of our responsibility to pray that we not enter into temptation. It is part of being vigilant.
All of these things—the roaring lion, the resisting, the afflictions, suffering, persecution, perfection, and strength—are related as parts of operations that fulfill God's purpose for us. We have to begin by understanding that Satan—despite his incredible intelligence, cleverness, and power—is still yet an unwitting dupe in God's hand to bring about His purpose. God is far more powerful than Satan. As great as is Satan's power over us, God's is far greater over Satan.