David is surrounded by a greater number than is actually physically surrounding him. His grief of heart is eating him alive, and he has great discouragement surrounding him. Selah means pause and consider. They then would tune their stringed instrument to another key. The devil will always be the voice of discouragement. God is always the voice of encouragement. With faith in God, it doesn't matter what the devil can do to us. The worst he can do is kill us, but if we're saved, we know we're going to be in Heaven.