I actually get the feeling Golovkin knows something a lot of people don't.
He's very confident about this fight. He seems a nice guy and talks about how its a 50/50 fight obviously to sell it but he comes out with some things like "i'll see you tomorrow" and after one fight he said "bring him, i'll show you" - He never usually speaks like this that much. I get the feeling he genuinely thinks/knows he can really whoop Canelo. All fighters think they can win of course, but they're also knowledgeable about boxing and probably have a fairly good idea if it's going to be a tough one, or if they just have the other guys number. I think GGG genuinely feels he has Canelo's number in this one.
Champion's mentality.
He knows it's a tough fight, he doesn't have to lie to himself about how he'll surely knock him out, or visualize it before sleep. He know he just has to remain calm and 100% focused.