I think the most challenging part of bpd is the lack of emotional permance. I wake up forgetting the day, month, and year before, and when I'm suddenly suicidal it surprises me and i assume it'll never get better, and that feeling is all i know and remember. when I'm really happy, when everything's perfect, i assume there's no way I'll be sad again or react emotionally to ever ruin what's making me happy. but as things come up, they go down too. everything in life is either the end of the world or the creation of everlasting euphoria.