Ephesians says, "we battle not against flesh and blood, but its powers and principalities of this dark world." Scripture also says we fight with weapons that are not of this world. Our weapons have divine power to demolish strongholds.
What kinds of weapons do we have? We have the power of prayer. We can petition our good God who hears us. We have the helmet of salvation, the breastplate of righteousness, the shield of faith which can quench the fiery darts of the evil one. We have the sword of the Spirit, which is the Word of God. We have the belt of truth. Our shoes are prepared with the Gospel of the readiness of peace.
Whenever selfish desires come our way, we should say: "I was expecting you. Greater is He that is in me than he that is in the world." And then, you fight back. You have been prepared. You already sought God and you know His strength is with you. You stand your ground.