I lay down and slept;
I awoke, for the LORD sustained me.
I will not be afraid of ten thousands of people
Who have set themselves against me all around.
As evidence of God's blessing both of these were used by David. Due to the intense pressure arising from the circumstances of Absalom's rebellion, sleep was considered a blessing to David. Many of us don't even consider sleep a blessing as great as David did in this circumstance. However, David slept, regardless.
Now waking was also considered to be a blessing because many people thought or wondered, "Would David live to see another day?"
"Truly it must have been a soft pillow indeed that could make him forget his danger,
who then had such a disloyal army at his back hunting of him."
(Gurnall, cited in Spurgeon)
Many times we take it for granted, but The Lord sustains us in our sleep. Take a minute to think about this... You are asleep, you are unconscious, dead to the world so to speak, yet, your organs operate, you breathe, your heart pumps.
Not maybe sustain us, or "I'll think about it" sustain us, but WILL. That's a guarentee! Praise you Lord!
David could stand against any foe. Why? Because God was sustaining him!
God knew the truth of Romans 8:31 before it was even written.
If God is for us, who can be against us?