1 Corinthians 15:33:

Be not deceived: evil communications corrupt good manners.

See also:

Faith in the Word and the Spirit of Faith
Dealing with Fear
Three Strikes Leave You Out
Sickness as Chastening and Judgment in the New Testament
Does 2 Timothy 3:5 Forbid Associating with Non-Spirit-Filled Christians?
Mistake: Disobedience