Proverbs 24:33-34 A little sleep, a little slumber, a little folding of the hands to rest— (34) and poverty will come on you like a thief and scarcity like an armed man.
I was in my early twenties when this verse hit home! It applies to ordinary life and work but also to the spiritual life. I read Biographies of servants of God who were very disciplined about their daily habits. Many would rise early for prayer and fellowship with God our Father. Hudson Taylor – a family man, would spend a couple of midnight hours with God so that his ordinary family life could be maintained. Good examples.
I believe that this proverb links with New Testament teaching about our spiritual lives:
John 9:4 As long as it is day, we must do the works of him who sent me. Night is coming, when no one can work.
Ephesians 5:14-16 This is why it is said: “Wake up, sleeper, rise from the dead, and Christ will shine on you.” (15) Be very careful, then, how you live—not as unwise but as wise, (16) making the most of every opportunity, because the days are evil.
The challenge is to keep awake (in the day) and make sure the robber doesn’t take away your opportunities to learn from and to serve the Lord Jesus. Maybe it is not challenging an occasional cat nap but is advising against that careless lazy feeling about spiritual things.