I believe it was the comedian Flip Wilson in his television show would say, "The devil's gonna get you?" Do we really know who the devil is, and how it is that he gets us? Ole Flip never answered that question, but the Bible does.
First, we know that he is a tempter. Just look what he did to Eve in the garden back in Genesis 3. How he enticed her and caused her to sin. The devil is still a master of temptation today. Especially for the Christian, he wants to bring them back into his kingdom. He is an ever threat (1 Thessalonians 3:5).
Yes, he rules his world, too (John 12:31). The ruler of darkness of this world is he that we fight our battles all the day long. "For our wrestling is not against flesh and blood, but against the principalities, against the powers, against the world-rulers of this darkness, against the spiritual hosts of wickedness in the heavenly places." Ephesians 6:12.
This active, living being that is fallen of God is a threat to us all for he is a liar. "...He was a murderer from the beginning, and standeth not in the truth, because there is not truth in him. When he speaketh a lie, he speaketh of his own: for he is a liar, and the father thereof" John 8:44.
Not only that, but he is the enemy of God and man. Remember the parable of the tares of the field in Matthew 13, the devil is the one that sows that bad seed among the good seed of Christ. We see how this enemy will be handled in that the tares will be bundled up and burned in the fire.
He is our adversary, "Be sober, be watchful: your adversary the devil, as a roaring lion, walketh about, seeking whom he may devour," 1 Peter 5:8.
Are you using sound judgment and watching so the devil won't get you?