Not exactly the same situation, but I left my old job for a better job and I was really distraught over disappointing my boss. We had a habit of getting lunch together and grew closer professionally, but it was her idealization of loyalty as a virtue and the intensity of the job that made me ruminate and ruminate too much. Looking back, I was too wrapped up in it and I just needed to make the choice that was right for me and not put other people's feeling or the organization first. As important and talented as you may be, your job will survive without you. As scary as unemployment may be, your boss mistreating you is a symptom of organizational failures. If you haven't tried advocating for yourself yet or having a conversation about it, I would do that before quitting or start actively searching for another job first. Action alleviates anxiety. But there's no need to feel bad about wanting better things for yourself.