I lie down and sleep; I wake again, because the LORD sustains me. I will not fear though tens of thousands assail me on every side. (Psalm 3:5-6)David knows that he has many enemies that are out for him, including his own son. Many people are saying that he will be found and killed, that God will not deliver him. Yet in this Psalm he still praises God and calls out to Him. Not in anger or bitterness, but with a trust that God's sovereign will is perfect and planned.
If I was hounded by "tens of thousands" who wanted me dead, I don't think I'd be able to say or do what David did in verse 5. He is unafraid! He goes to sleep, peacefully, and with complete trust in God, wakes up remembering and believing that God sustains every moment of his life. If he wakes up in the morning, it is only because of God's will that he does so. Because there must be a reason for why he wakes up day after day.
David wakes up with the thought that he is awake and alive because God has a purpose for him. Not just in the long run, as in "God's will for my life," but that there is a purpose to be lived out each day. How often do I wake up each morning believing that each day is an opportunity from God?