Keep a song in your heart.
How does complacency affect our spiritual life? Complacency grows out of a false security that creates a lukewarm faith. It's in the Bible, Revelation 3:15, NIV. "I know your deeds, that you are neither cold nor hot. I wish you were either one or the other!"
Complacency can eventually destroy us. It's in the Bible, Proverbs 1:32, NIV, "For the waywardness of the simple will kill them, and the complacency of fools will destroy them."