You don't have to change if you really don't want to. You can be bitchy and blame all your problems on the people around you, and let jealously and self-pity and fear shrink your miserable little life until you've driven away anyone who ever cared about you and are finally at peace, completely alone. No one can stop you if that's what you really want. You are not obligated to get better.
But you do have to accept the consequences of that decision, whatever they might be, because choosing not to healz whatever healing looks like for you, will always cost you dearly. I was wrong before. You can't live trapped in your trauma, you can only survive. And surviving is not the same thing as living.
Mary smashes in the face of a manifestation of trauma with her own manifested trauma, which destroys both, to save her own life and she lives because she decided the fear and uncertainty of being alive was more important to her than dying safe in her misery, even if part of her will always be that scared little girl trapped by her own mother's choice to rot in her trauma.
Clark admits that he doesn't want to change, because it's scary and hard and he'd rather just keep blaming the world for his problems, and then tries to embrace his trauma like he always has, and it immediately destroys him.
You do have to face your trauma, you have to go in there and it's scary and horrible and terrifying, the man at the end was right, it is important, but you cannot stay. Staying is death. At some point "just learning a little bit more" turns into rumination and rot. Your empty may halls echo with grand self-mythology, but they're still empty. And you cannot stay there, tracing the same cracks in the stone and lines on the walls over and over, refusing to see what they're actually telling you, without it costing you everything.
What a movie, man. What a fucking movie.