What does “Bad association spoils useful habits” mean?
It means that a person who associates themselves with the wrong type of people will start developing their bad habits rather than your good habits rubbing off on them. For instance, if child A is raised in a home where values such as not using profanity, not using illegal drugs, and so forth …… and they begin spending time with child B whose parents have not instilled those same values in them, then the most likely result is that the bad habits of child B will begin showing in child A. So for Jehovah’s Witnesses, who value God’s moral laws and principles as set forth in the Bible, if they were to choose to begin associating with people who didn’t have that same value for God’s laws…….eventually the other people’s bad habits would begin to rub off on the Witness and could cause the Witness to let down their guard.
Well in a religious context I would think it would mean if you have useful habits, like praying everyday or reading your scriptures regularly or keeping the sabbath day holy and you fall into the wrong crowd, they might convince you or you might be spiritually brought down so that you no longer want to continue those habits.