Okay, so, I said earlier to Robin, that Dean feels more comfortable and secure with people who have seen him at his worse and still don't leave. Which Ganymede has seen and still stayed, so Ganymede is probably Dean's best friend in camp! They have evolved to a point they can ramble out about anything and Dean is comfortable... with himself! There's no facades, no pretense, no need to be "better" than what he thinks he is, because Ganymede already knows everything there is to know and he's still there! So Dean is a lot calmer, zen when he's with Ganymede than he would be with anyone else! And Dean trusts Ganymede completely, there's no question there. He may think Ganymede has a few screw loose, but the trust is implicitly there.