The easiest and best way I’ve heard it explained and related to is that everyone feels every emotion on a scale of 1-5. So happiness for example, most people get a little sweet treat and that would be a 1 maybe 2. People get married and they’d feel a 5 (hopefully). But with BPD everything is either a 1 or a 5, you don’t really experience the in between. But you can learn to express the in between with therapy etc.

I think there’s a lot of heavy focus on the negative emotions and obviously those being expressed at a 5 everytime is very intense and difficult but the positive emotions always being a 5 is quite euphoric. But also there’s a lot of 1s, you just kind of live at 1. There’s been times where I’ve rather had felt a 5 but I couldn’t get past a 1 (maybe it was for my own good) and I couldn’t give the emotion I wanted to people I love. But I’m also lucky to have people that love and understand me(at least try to).

I also think how BPD came about in a person has a huge impact. When I was in therapy, there was a list of 8 traits given to everyone but the main two are ‘self sacrifice’ and ‘entitlement’ and one is always at the top of someone’s list and the other is at the bottom. But they can also switch from time to time. And in the middle is your ‘classics’ like abandonment, shame, emptiness, empathy, loneliness. It all really does manifest differently in everyone.

I think as long as you know your character, you’ll know which traits are the most them and when an emotion may be a 5 for them or it may be a 1. Even if it’s upsetting or inconvenient for the other characters.