When the enemy sees that you're turning away from darkness and drawing closer to God, he will do everything he can to discourage you. He wants you to doubt God's goodness, question His promises, and lose faith in His plan for your life.
The enemy knows who Jesus is and knows the power of God. ("What do you want with me, Jesus, Son of the Most High God?" (Mark 5:7) and they ask Jesus to send their spirit to pigs. They know Jesus has this authority) That's why he works so hard to distract, deceive, and discourage believers. His goal is to keep you from walking in the freedom, peace, and purpose that God has for you.
When you feel attacked, overwhelmed, or filled with doubt, recite this in your mind & rebuke the evil:
"You have no power over me. I am saved through Jesus Christ. My sins are forgiven. I am a new creation. I belong to Jesus, and you already lose the battle.”

"Therefore, if anyone is in Christ, he is a new creation; the old has gone, the new is here!" — 2 Corinthians 5:17