You are residing at a time when your enemy the devil (who is not in the lake of fire yet) is prowling around throughout the earth looking for someone to devour! His desires are to spiritually destroy another saint – devour him!
Be self-controlled and alert. Your enemy the devil prowls around like a roaring lion looking for someone to devour. (1 Pet 5:8)
The devil doesn’t get distracted from that goal. He continues to plot, scheme and tempt the saints. He is patient and clever and has a wide variety of allurements. Because Peter’s recipients were born again (1:23), he is definitely issuing this frightening warning to the Christians saved by grace! This is most serious! Peter wanted them to know they could yet get devoured by the devil and it was their own responsibility to protect themselves from getting devoured [swallowed in Greek] by the devil. Their safeguard against this was to be self-controlled and alert. The devil is known for tempting with sin. Why does he do that? Because he knows the deadly effects sin has on one’s spirit. The Bible says:
But if Christ is in you, your body is dead because of sin, yet your spirit is alive because of righteousness. (Rom 8:10)
Sin can change a Christian’s righteous standing before God and bring about spiritual death (Rom. 8:12,13). The unrighteous will not inherit the kingdom of God (1 Cor. 6:9,10). Elsewhere we are told to avoid every kind of evil (1 Th 5:22) and the Christian life is a struggle against sin (Heb. 12:4), but to do that we must know what is evil. This is all included in fighting the good fight as a good soldier of Christ Jesus and will bring persecution of some type because of separation from the world (2 Cor. 6:17,18) to keep yourself pure (1 Tim. 5:22). Being self-controlled will protect the saints from many spiritual snares and traps, but not all.
Being alert [watchful] is another issue and could include rejecting false teachings. False prophets and false teachers have always been a lethal danger to the Lord’s sheep. Though they are so deadly, they are not always readily known! That is why being alert [or watchfulness] is vital. We are to test the spirits and not just believe them (1 John 4:1). If one gets deceived through false teaching, he will be adversely influenced, even if he is self-controlled! We must be alert! There are doctrines of demons which are communicated to the saints by sincere and zealous people who are serving the devil unknowingly. Unless you are seriously resisting the devil by being self controlled and alert, he will take you down like he has Adam, Gideon, Jeroboam, Solomon, Judas Iscariot and many others! Remember that. GOD BLESS YOU.