Well I think the reason why that's a bad ending is because the protagonist got stuck in a belief or thoughts that no one will ever understand her illness, and resentment that everyone else seems to be living happily while she has to deal with and be limited by her illness. IT was not like OH and after that her life became so bad!! But just because you chose choices that led to her developing some toxic beliefs, feeling resentment, feeling upset no one will ever truly understand
I imagine after that she probably just continued to live her life and still managed the narcolespy, but having a very negative mental outlook or something.
It really reminds me of myself..