BQ: When we change our lives to more godly behavior, we often want to keep parts of our old lives around. What can be especially damaging is keeping bad influences, especially when we're not very strong ourselves. 

The Christians in Corinth ran into this problem and let some pretty scurrilous people remain a part of their lives, which led God to remind them that, "Don't you know that a little yeast works through the whole batch of dough?" (I Corinthians 5:6)  

When we change, we need to dedicate ourselves to having out with the old and in with the new. :)