Balancing Compassion and Self-Respect in Relationships

Well theres a point of the other person being upset that you need to draw a line with mostly. You're right to analyze what may be happening with them and give them some space to work out their issues and then bring up what was hurtful about the interaction by prefacing that you know they didn't mean anything but to avoid doing it again. If they say something hurtful when they're upset they need to take accountability for that and avoid doing it later, you're also not a mind reader and they can't expect you to know what's going on or help without them being open about it. The fact that you analyzed it enough to understand that it wasn't personal and expressed that you weren't upset with them just hurt by what happened clearly means you WERE considerate and if they want to elaborate their problems from that day they're free to but they should also acknowledge that if you were hurt they should avoid doing what they did, not everyone wants to own up to their behaviors from a bad day though. All you're asking is for your boundaries to be respected, that's not too much and no one should act like it is. If they continually refuse to change their behaviors and try to stop you from setting boundaries it might even mean that there's other motives than just a bad day or whatever and they may be taking their frustrations out on you intentionally. Obviously I don't know the full situation so i could be wrong but from the sounds of it you're already doing the right thing and the problem isn't you.