Good exists - a Catholic comments

[Bucky Ball]

Having a false belief about oneself is not a sign of madness nor was he a liar if he truly believed it.

As Mark would have it, Jesus did NOT believe that he was God.

Mark 10:18 And Jesus said unto him, Why callest thou me good? there is none good but one, that is, God.

Now if John says he did believe he was God, that's not my problem, that's the believer's problem.

Exactly. Precisely. The divinity of Jesus is different in each gospel. 
In Mark, Jesus "earned" his divine status. 
In Mark, he was a human, and not a pre-existing divine being. He was "raised" to divine status (later). He was not a divine being either pre-existing and not while on Earth. 
One of the theme's in Mark is "the Messianic Secret". He earned divine status and was raised up later. These concepts are Bible 101 in any mainline university Biblical Studies program.