No one is perfect. We do things that we know are wrong, and then feel terrible about it. The way to get over it is to turn to the Savior. Knowing that the Lord compared Himself to a shepherd, who would willingly leave his other ninety-nine sheep to find the one that is lost, tells us that each individual — no matter who they are or what they did — is important to Him.
The setting of Black Lamb is in the area around the Sea of Galilee. A young lamb as this one, if lost, would surely die. Similarly, if we lose our spiritual way, we will not return to our Father in Heaven. Instead however, this once-lost lamb is going home, back to the fold, where it will be safe and loved.