I have BPD (borderline personality disorder)
The most noticeable part of it is that my emotions react really quickly and really strongly. Like I can be calm and feeling fine and then something bad might happen and I'll be catastrophically upset and ready to kill myself 30 seconds later.
"Splitting" as well, where something is either "good" or "bad" and there is no middle ground. My brain can "split" someone from good to bad in an instant. Like I can be friends with someone and love them and then if they say or do something wrong then I can wish they were dead or hate them moments later. It's exhausting, going from loving to hating people and back again so quickly.
Fears of abandonment are big too, I'm always so scared that everyone in my life is going to discard me once they get what they want from me, and if I feel like I'm being abandoned it causes an extremely strong reaction like I said above.
Impulsiveness and self destruction is another part for me, especially for self harm, drugs, and excessive spending, DBT skills have helped me get it under control but it's still often on my mind.
Another BPD symptom I experience is feelings of emptiness, I always either feel numb and empty or extremely emotional, and there doesn't seem to be a middle ground. My emotions are either 0 or 100.
And finally probably an unstable self image. I don't know who I am, I don't know what I am. Everyone knows a different me, there is no real "me". I change every aspect of my personality from how I talk to my favourite food if I think it will make someone like me. It makes me feel extremely manipulative but it comes as instinct to me. Some days I feel like being a pretty, carefree summery girl and the next day I might want to move to Berlin and become a heroin addict, just for fun.
BPD is not a lot of fun to have, although sometimes it can feel like it when you're in the moment.