Vader does more than just take a load off inside his pressurized chamber (that accidentally sounded really dirty for some reason). If it really is a place of meditation, then perhaps he has time to think about all the Jedi he’s murdered over the years.
This piece by Jeff Carlisle has Vader facing down his demons. Or rather, not facing them. I see Mace Windu there, and tall head guy from the prequels, and girl Yoda. He killed girl Yoda?? No wonder regular Yoda is pissed.