Be Alert

The Bible says Christians are aliens in this world (1 Peter 2:11). It as if we are soldiers dropped behind enemy lines. Any soldier in enemy territory would not last long if he did not keep alert, with his defenses up and his weapon ready.
God has provided us with the armor and the weapon. Our weapon is the Word of God, also called Jesus in John 1:1. Jesus is the Truth (John 14:6). It is the truth of Jesus that defeats Satan and his demons every time.
According to Neal Anderson in his book Victory Over the Darkness, our battles with the enemy should not be power encounters, but truth encounters. Just as Jesus rebuffed the devil’s temptations with Scripture in the wilderness (Luke Chapter 4); so are we to defeat the defanged liar with the truth of Jesus.  It is the truth, not shouting or emotion, for which Satan has no counter-attack. We speak it; he flees.

This is another reason it is so important to understand our true identity in Jesus. Those who do not know the truth cannot call upon it. And believers interceding for non-believers provide at best temporary respite from attacks of the evil one upon the unsaved. (Matthew 12:45)
Ephesians 6:10-18 describes our armor this way:
“Finally, be strong in the Lord and in his mighty power. Put on the full armor of God so that you can take your stand against the devil's schemes. For our struggle is not against flesh and blood, but against the rulers, against the authorities, against the powers of this dark world and against the spiritual forces of evil in the heavenly realms. Therefore put on the full armor of God, so that when the day of evil comes, you may be able to stand your ground, and after you have done everything, to stand. Stand firm then, with the belt of truth buckled around your waist, with the breastplate of righteousness in place, and with your feet fitted with the readiness that comes from the gospel of peace. In addition to all this, take up the shield of faith, with which you can extinguish all the flaming arrows of the evil one. Take the helmet of salvation and the sword of the Spirit, which is the word of God.  And pray in the Spirit on all occasions with all kinds of prayers and requests. With this in mind, be alert and always keep on praying for all the saints.”