Matthew 5:4 KJV
Blessed are they that mourn: for they shall be comforted.
To truly know the need for comfort, one must know what true mourning is. When we mourn over the state of our sin and realize how terrible we are, only then can we receive God's comfort/forgiveness.
I mourn over my sin. I mourn over the lost time to truly serve God. I mourn over the lost opportunities to do His will. However, I know that God forgives me and gives me hope to do better. I know He can and will use my mistakes for His honor and glory. I take comfort in knowing I am forgive and can still be useful in God's hands.