The rich young man may have been sad because he decided that following God was too costly, and he now knew that he could not be perfect. This is how people often interpret the story, but it does not make much sense. This interpretation gets stuck in our head, perhaps even preventing us from hearing the Word of God. The rich young man followed the commandments, but he knew something was missing. When he realizes that Jesus has the answer he is seeking, he does not walk. He runs to Jesus, kneels down before him, and asks a question. How different this is from the questioning of the Pharisees! He is not testing Jesus; he actually wants to know something. Is it likely, then, that when he gets the answer he has been seeking, the answer that he ran and knelt down for, he gave up?
The reason why the rich young man went away sad was because he thinking of all those possessions that he was about to lose. This is an excellent feeling, the feeling of ripping out something which has put down roots in your heart. This is a pain which few pleasures can equal: giving something up to follow God. To be a Christian requires a certain kind of masochism. We take pleasure whenever God presents us with the next cross. Something stands in our way, we lose a possession, we are treated unfairly, we are spit upon, the very thing we thought was in our grasp is stolen away. The first feeling, the human feeling, the natural feeling is sadness, anger, despondency. Then, either we embrace the feeling and become consumed by it, or we embrace the cross and find joy that nothing can equal. The martyrs are not remarkable because they die for the faith; lots of people die for all kinds of nonsense. The martyrs are amazing because they die joyfully.
As for the rich young man, longstanding tradition tells us that he sold everything, gave it to the poor, and followed Jesus, that he there in the garden when Jesus was arrested, that he continued following Jesus as they took him away, but, when they tried to grab him, he was wearing nothing but one cloth and he left that in the guards’ hands and ran away naked, that he followed St. Peter around as an assistant, and then wrote a Gospel, this Gospel, according to Mark.