The third advent candle is the Angel Candle. The angel candle represents that message that the angels shared the night of Christ's birth. Part of that message was the message of God's universal appeal of grace through the Christ child.
When going through difficult times we may assume that the trials we are facing are God’s punishment of us. While that may be true on some occasions, it may also be true that we are experiencing the effects of being in a fallen world.
David, unlike many of our gilded appraisals, was far from the perfect person. So what did it mean to be "a man after God's own heart." It is never about the person themselves. It is always about God's ability to use the broken and imperfect to accomplish His purposes.