The son comes back from squandering his portion of the estate on hookers and booze. He says to himself, There’s no way my father will take me back as a son, but perhaps he will take me back as a servant.
He’s wrong of course, and this is the Christian story’s difference. You aren’t asked to approach as a beggar, as a servant, but as a child.
The Spirit we receive does not make us slaves, but heirs of God and co-heirs with Christ. Or to put it another way, not servants, but sons.