In Psalm 6 & 7, David cries out honestly and sincerely to the Lord. David experiences his emotions and brings every single one to the Lord. He trusts God wholeheartedly and knows He is trustworthy and faithful. He brings every pain to God and every joy as well. He talks with God all day every day humbly and submissively. He doesn't try to take matters of his enemies into his own hands. Instead, he trusts God to handle it. God's love is a holy love. He is perfect, pure, righteous, and just. God gave His own Son to die for the sins of the world upholding His own holy law and at the same time, offering us His loving mercy and compassionate grace. It's up to us to choose to repent from our selfish selves and receive His offer, to receive Him - heart and soul.