Sully thought he was about to go and have a lovely time in Hogsmeade and get completely smashed. He THOUGHT. But he thought wrong.
And being Sully, and being so set on going, among other things, cue an EPIC meltdown. It wasn’t red mist he saw this time so much as a red curtain and he threw himself the invisible barrier keeping him in the castle a few times, kicked it and beat at it with his arms (all while swearing profusely) and tried some spells but it all did nothing. He went through this cycle a few times before finally giving up, exhausted and limped back to the common room angrily trying to explode things on his way back. He also took his frustration out on a couple of armchairs (enjoy the show, younger years!) before going to bed and trying to finally sleep.
If anyone tried to stop him, (he wouldn’t notice who) he would push them away and tell them to fuck off.