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. (Ephesians 6:12 NIV)

But the fruit of the Spirit is love, joy, peace, forbearance, kindness, goodness, faithfulness, 23 gentleness and self-control. Against such things there is no law. (Galatians 5:22-23 NIV)

15 I don’t really understand myself, for I want to do what is right, but I don’t do it. Instead, I do what I hate. (Romans 7:15 NLT)

1. Demons are real.

Be alert and of sober mind. Your enemy the devil prowls around like a roaring lion looking for someone to devour.(1 Peter 5:8 NIV) 

2. We can be under their influence. 

26 “In your anger do not sin”: Do not let the sun go down while you are still angry, 27 and do not give the devil a foothold. (Ephesians 4:26)

15 See to it that no one falls short of the grace of God and that no bitter root grows up to cause trouble and defile many. (Hebrews 12:15)

14 For if you forgive other people when they sin against you, your heavenly Father will also forgive you. 15 But if you do not forgive others their sins, your Father will not forgive your sins. (Matthew 6:14 NIV)

3. Demons flee at the name of Jesus.

However, do not rejoice that the spirits submit to you, but rejoice that your names are written in heaven.”

Submit yourselves, then, to God. Resist the devil, and he will flee from you. (James 4:7 NIV)

3 For though we live in the world, we do not wage war as the world does. 4 The weapons we fight with are not the weapons of the world. On the contrary, they have divine power to demolish strongholds. (2 Corinthians 10:3 NIV) 

We demolish arguments and every pretension that sets itself up against the knowledge of God, and we take captive every thought to make it obedient to Christ. (2 Corinthians 10:5 NIV)