I resisted the urge to text my soon to be ex husband, "you are a f@#king a$$hole!" (without the censoring, of course.)
Hi talking rose, yes, that sounds like the sort of thoughts that come to the surface when angry, and yes, it's a normal stage to go through while grieveing an event like this.
I think you did the right think by resisting the urge, this is really important. It shows a key difference between a pwBPD and "norms", we are able to process the emotion, feel the emotion, without acting on it. This not acting out, is so important in maintaining good emotional health... .if it is acted out, if you send the text, the likelihood is that you'll great for a short time, but then realise that to hurt others, no matter what they have done to you, does not of itself bring you happiness or self respect.
pwBPD sometimes cannot manage or control their emotions, hence the tendency to impulsive behaviour (such as the sudden discard for example) because they cannot process the emotion they feel.
If the anger hangs around longer than you want, then you may need help processing it, and there are many ways to do that, journaling, talking it out with a friend (or therapist), exercise, etc... etc... .
For me, the anger came in waves over a period of a few months and then gradually diminished, and so long as there are no triggers, I no longer feel anger towards my ex, though I do sometimes wonder how the hec could she have done this, that or the other, and then I remind myself... .because she is disordered and that is what being disordered means.