Discipleship is about values.
This could not be clearer in the Gospels. Jesus' call is for a double action: leave and follow. "Follow me, and I will make you fishers of men," he first said to Peter and Andrew in Matthew 4:19. And "Immediately they left their nets and followed him." Then to James and John. And "Immediately they left the boat and their father and followed him." Whether nets or family, the call to follow Jesus is the call to walk away from something else. It is the call to this, not that. Here, not there.
Getting to the Root
The disciples knew this. They knew they were forsaking one thing for another. And they knew pleasure was at the root. That's why Peter asked what he did in Matthew 19:27. To be sure, he was still putting the pieces together, but he tipped his hand here. He was waiting for the pay off. Jesus had just taught on riches, which I imagine seemed out of the ballpark to Peter. Riches? Psssssst! (He had even walked away from his meager livelihood.) Ayhem, Jesus? Great lesson on riches, and about that, we, you know, we, uh, we left everything. So when do we get to cash the check?
Maybe more astonishing than Peter asking the question is that Jesus answers him.
Forsake the lesser pursuit in order to gain the greater pleasure. That's why a man sells everything to buy a field (Matthew 13:44) or why the merchant considers all his goods mere commerce compared to one pearl (Matthew 13:45). There is something better out there and discipleship is the great calling to lay hold of it.
That Found Treasure
The human is a deep creature: "not just a body, but a soul. Not just a soul, but a soul with a passion and a desire. Not just a desire for being liked or for playing softball or collecting shells." And Jesus says, "Follow me." His call harmonizes with our inherent depth. Look, here's the treasure. It's me. Then we are awakened, muddy hands and all, wallowing in the slums this whole time but now testifying of a "desire for something infinitely great and beautiful and valuable and satisfying — the name and the glory of God" (Boasting Only in the Cross). So we leave and we follow. Goodbye broken cisterns (Jeremiah 2:13), hello my exceeding joy (Psalm 43:4).
We follow Jesus into a new world, not as mere pedagogy, but as fellowship. We come not as objective pupils, but as rebellious creatures made alive for the first time — rebellious creatures now reconciled to God by the death of his Son.
Discipleship — following Jesus — is to live before God's face, to dwell in his presence, to be satisfied in all that he is. We follow as creatures of grace, entering into the fellowship of the triune God in whose presence there is fullness of joy, at whose right hand are pleasures forevermore (Psalm 16:11).