How Much "Just Like the World" is too much....?

This whole idea of how much is too much has always wandered through the deep recesses of my mind. How close can you get without getting burned? How much can you do without crossing the line? How far is too far? These types of questions and the many variations have been asked by lots of folks who call themselves "Christians" and personally, I think the question itself may be a red flag that needs to be paid attention to, rather than the subject of the question explored or answered. If we are "Christians" (Christ followers), why in the world would we be asking how close to the enemy can we get, or how much of the enemies favorite temptations (or those of our own lust) can we play with and still be "okay"?
The heart of the matter....oops, said it already...YES, the HEART IS the Matter! Consider Jesus' statement about defilement in the Gospels...paraphrased roughly: its not what goes into your mouth that defiles you, but that which comes out from the heart. Ouch...wait, you say..."that stuff just slipped out and you know, we are not perfect after and by the way, who made you the judge?" Ah, more indications of a heart condition, perhaps even a critical heart condition. 
Consider a little scenario with me; a young person who grew up in church, professed their belief in Christ and claimed His salvation decided to follow the example of their parents in rebellion and left with them. The young person was old enough to make their own decision and stand on their own two feet, but chose to follow the apostate group off into the wild blue yonderish part of another town and church group. The wonderfully welcoming pastor and his family, in that new town and church, swung wide open their arms to embrace this family. Choosing to ignore the issues of church discipline presented to him (the pastor), for the sake of having new folks to help and grow his church, he readily assimilated this family and the young person into all aspects of life and ministry. Ignoring all Scripture and God's template for the New Testament Bible believing church, they instead also formed deep family relationships with this family and young person. The young person moved away but maintained contact through social media and visits. Over time the young person's actions (complete abandonment of christian fellowship while out of town), attitude (immersing themselves into the world and the vices thereof) and language (profusely effluent in the manner of James 3) turned worse and worse. But because a relationship had been formed, in spite of the warnings and caution, the new church and its pastor only chose to see what they wanted. The young person was "godly" when visiting and communicating at church or family events, but worldly, JUST LIKE THE WORLD, all the rest of the time. And this brings the question, "how much is too much". 
Well, Scripturally, its not looking too good for our example. God requires a heart surrendered to Him....not just loaned at special occasions. He wants a disciple in the Body of Christ, not a tumor growing on the surface. 
Too much is the first step, the first thought, the first touch and whatever else may pull us from complete devotion to the Jesus. It is not a matter of how far can I stray, rather it is HOW CLOSE CAN I GET TO JESUS? Everyday, all day and for ever. The closer we remain, by His power and direction, the further from the pull and staining of the world we will be. Only THEN, will we be in the world, but not OF the world!!