"For the weapons of our warfare are not carnal, but mighty through God to the pulling down of strong holds;
Casting down imaginations, and every high thing that exalteth itself against the knowledge of God, and bringing into captivity every thought to the obedience of Christ;" - 2 Corinthians 10:4-5
Through careful strategy and cunning deceit, Satan attempts to set up "strongholds" in our mind. A stronghold is an area in which we are held in bondage (in prison) due to a certain way of thinking. Strongholds are lies that are believed.
The aposlte Paul tells us that we have the spiritual weapons we need to overcome Satan's strongholds. Using our weapons, we refute the enemy's lies, arguments, theories, reasonings, and every other thing that tries to exalt itself against the truth of God's Word. We must take our thoughts captive and refuse to indulge in the fleshly luxury of receiving and meditating on every thought that falls into our heads.
The primary weapon with which we do battle is the Word of God used in various ways -- preached, taught, sung, confessed, meditated upon, written, and read. We must get the knowledge of God's truth in us to renew our minds. The Word of God has a cleansing effect on our minds and lives any way we use it.
No one will ever live a truly victorious life without being a sincere student of God's Word.