Pray hard and believe you have what you pray for. Yet, leave room in your mind for God's will and purpose. His thoughts and ways are higher than our thoughts and ways.
David had sinned greatly and kept it quiet. Because of his silence his strength has been drained. Then the prophet Nathan showed him his sin. He confessed it and was forgiven. God forgave his sin and the guilt of his sin. We all need to have this attitude about sin.