The truth of the matter is that the devil and all his weapons like discouragement, defeat, depression, doubt, etc. have already been defeated. The Lord Jesus Christ won the victory for us and has already defeated the enemy satan (Colossians 2:15). This victory however needs to be enforced from time to time especially in our minds since that’s where satan attacks us (2 Corinthians 10:5).
The biggest weapon to overcome defeat, depression, doubt and anything else from the devil is praise. Isaiah 61:3 talks of the garment of praise instead of a spirit of despair. Psalm 8:2 describes praise as a weapon to silence the foe and the avenger. Praise is ordained of God to defeat satan and all his intents and purposes against the believer. Praise will silence the foe and the avenger. That means when you begin praising God it will immediately silence satan and not a peep will come from him. The problem with most people is that they want to fight satan with wrong weapons or their own weapons and when they end up losing then they begin to blame God or say God’s Word does not work. God’s Word clearly states that we battle not against flesh and blood (Ephesians 6:12) and also that our weapons are not natural but are spiritual. Praise is a spiritual weapon and that too a mighty one. Other weapons are prayer (spiritual that is and not prayers in the flesh), Word of God, praying in tongues, etc. A more complete listing is found in Ephesians 6.
To put it in more practical terms, a couple of nights ago (or early morning around 2 am) I woke up with symptoms of bodyaches and fever. What I mean is fever and bodyaches were knocking on my door. I have learned in my walk with God that it is up to us whether we open the door to satan or shut the door on him. I have always shut the door on satan! Now how the door is shut differs from person to person. Most people I know deal with the devil by speaking to him and commanding him in Jesus’ name. This is not incorrect and is also Biblical, but there is a better way too. The better way is to begin praising God. Praising God will strike terror into the enemy’s heart and send him running in seven different directions (Deuteronomy 28:7). Yesterday night when the satan knocked on my door with fever and bodyaches I turned on the weapon of praise and began to praise God the Father, the Son and the Holy Spirit. Fever and bodyaches which had come knocking on my door fled in 7 different directions (or more) and in under a minute. Praise works!