I don't think it does just happen naturally. Certainly, I think we could develop our Christian character a lot more with consciously-planned activities, materials and support systems. I'm with Dallas Willard (again...) on this one. In a passage from page 344 of The Divine Conspiracy noting the lack of intentional, planned discipleship in churches, he says this:
Imagine, if you can, discovering in your church newsletter or bulletin an announcement of a six-week seminar on how genuinely to bless someone who is spitting you... Or suppose the announced seminar was on how to live without purposely indulged lust or covetousness. Or on how to quit condemning the people around you. Or on how to be free of anger and all its complications.
Willard goes on to invite the reader to imagine a church sign that says 'We Teach All Who Seriously Commit Themselves to Jesus How to Do Everything He Said to Do'. Isn't that what our churches should be all about?