Psalm 3:1 & 2
"O Lord, how many are my foes! How many rise up against me! Many are saying of me, 'God will not deliver him.'" NIV translation
He just calls out to God by sharing the hurt that is on his heart. It is bad enough that a group of leaders have abandoned him but they are even led by his own flesh and blood. They were even saying that God would abandon David. Although we may not be able to relate to being a king and having this happen, many parents face the rebellion of their children. The rebellion may not be as severe as this but our reaction should be the same and that is to call out to God. We must also remember that we, too, rebelled against our Father who is in heaven so He knows and understands what we feel.
"But you are a shield around me, O Lord; you bestow glory on me and lift up my head." NIV translation
David continues his praise by remembering that God is his protection from the schemes of men. Not only that, but, God also lifts up His people and brings them honor in the face of those who mock what the Lord has done.
"To the Lord I cry aloud, and he answers me from his holy hill. Selah" NIV translation
David knew that he could take all of his worries and cares to God through worship and prayer. As God's children, He listens and answers us when we call out to Him.
"I lie down and sleep; I wake again, because the Lord sustains me." NIV translation
David understood that God controlled everything and even gave him the ability to sleep and to wake to a new day. When we realize that God is in charge of even those small details in our lives, then we can easily trust that He will handle the bigger things that we face.
"I will not fear the tens of thousands drawn up against me on every side." NIV translation
Because of the fact that he knows that God sustains him, it does not matter how many join forces against him. The Creator of all things is on his side and He has the power to handle the situation. The same is true for us as children of God in that we do not have anything to fear no matter how bad the situation appears in our sight.
"Arise, O Lord! Deliver me, O my God! Strike all my enemies on the jaw; break the teeth of the wicked." NIV translation
David asks God to not only defend him but to also go on the offensive on his behalf. These people have risen up against God's appointed king and David wants God to attack them for their wickedness. He doesn't ask God to kill them but only to slap them and wake them up and to make their attacks on him ineffective by breaking their teeth. Even in this, God's mercy will be demonstrated.
"From the Lord comes deliverance. May your blessing be on your people. Selah" NIV translation
David knew that his only hope was in God and His intervention on David's behalf. David ends this worship with a prayer for God to bless the people. Even during the betrayal of his own son, David (the father of the nation) prays for others.