As a Christian, we are engaged in an ongoing spiritual warfare, whether we're aware of it or not. From the moment you gave your life to Christ, you were transferred from the kingdom of darkness into the Kingdom of God's dear Son according to Colossians 1: 13. That transfer alone makes you a target of the devil's anger.
Before salvation, we were under Satan's influence. But now that we belong to Jesus, we're threats to his agenda. That's why he is angry with true believer. And his mission remains unchanged, which is "To steal, to kill and to destroy". The Bible warns us in John 10:8, it says;
"Be sober, be vigilant; because adversary the devil... walketh about, seeking whom he may devour"
Note that this isn't a matter of if the enemy will attack, it's a matter of when! He is always on the lookout for moments when we drop our guard, catching us off guard, through distraction, compromise, fatigue or spiritual laziness. But when we remain vigilant, his plans fail.
This means we must live with spiritual awareness, not fear. Satan complained to God, in Job 1: 10 that, he can't touch Job because God has placed a hedge of protection around him. This reveals something vital: The devil cannot touch you unless you break the hedge through disobedience, carelessness or unbelief.
Ecclesiastes 10:8 (NIV) - "Whoever breaks through a wall may be bitten by a snake."
We are advised to stay within the boundaries of God's love, obedience and truth. As long as you're aligned with Him, the enemy may roar but he won't prevail