Ok here's my take. It's what the disciples felt about Jesus after John 6 and the eat my flesh, drink my blood speech. They had to acknowledge we don't understand a single word He says. But He's still our Dude. And from now on, we'll drink His communion wine. (John 6:68)
The rest of the song has nothing to do with Jesus. But I can imagine Peter had a lot to confess.
And at the end of it all, Jesus gave everyone reason for Joy to the World.
And I just completely made all this up because I thought it was funny.