"And be not conformed to this world: but be ye transformed by the renewing of your mind, that ye may prove what is that good, and acceptable, and perfect, will of God." - Romans 12:2 (emphasis mine)
That's the key, "the renewing of your mind". It definitely takes work, but there's a really good reminder in Philippians 4:8 - "Finally, brethren, whatsoever things are true, whatsoever things are honest, whatsoever things are just, whatsoever things are pure, whatsoever things are lovely, whatsoever things are of good report; if there be any virtue, and if there be any praise, think on these things."
Keep up the fight, I know it can seem hopeless at times; generally when it looks the darkest, that's when the enemy is running scared, throwing the last he's got at you, so you know you're on top if you'll just keep it up.
-Jon