I will both lie down in peace, and sleep

The cause of David's confidence that he will lie down in peace and sleep (Psalm 4:8) is not that all things were going his way. He was in fact being humiliated (v. 2a), lies were being spoken against him (v. 2b), there were provocations to anger (v. 4), and he was getting negativity and discouragement from many (v.6). David's first response to all this, is to cry out to the Lord (v.1a). We don't know the occasion of the Psalm, but we do know that David had lots of troubles, and this is not likely the first of them (v 1b). There were times when his soul was overwhelmed within him, and on such occasions he would pour out his complaint to the Lord (Psalm 142:2, 3). And as here, he is confident the Lord will hear him, comfort him, and deliver him (vv. 3b, 1b, 8b).

But David knows he has a part to play in all of this, and he instructs himself and us in what to do at such times. In particular, though we may be angry, we must not sin in our anger (v. 4b). He sees this as offering a sacrifice of righteousness (v. 5a). The scriptures know us well, when we are angry our immediate desire is to retaliate. Resentment rises, and the evil one whispers to us that if we let go of the resentment, they will get away with it. So it is indeed a sacrifice (a putting to death of the resentment) to respond righteously, and to leave it to the Lord to whom vengeance belongs (v. 5b; Romans 12:19). We must replace the anger by meditating, and by being still and knowing that He is God (v. 4b; 46:10).

Not saying that this is immediate or easy, but when, with His help, we have wrestled though these things, we will be able to say with David "You have put gladness in my heart" (v. 7a). And we will also be able to "both lie down in peace, and sleep" knowing that "You alone, O LORD, make me dwell in safety" (v. 8).

Father, we need Your help Lord. Thank You that Your grace is enough. Thank You for peace,  and that You give Your beloved sleep (Psalm 127:2) in Jesus Name Amen