Why does a threat to my job feel like a threat to me?

You are noticing something important: your sense of who you are and your job have grown into each other, so a threat to the work lands like a threat to your very self. That is why a bad review or a rumor of layoffs can feel like the ground disappearing. It isn't drama. When two things are fused, an attack on one really is felt as an attack on both. The good news is that noticing the fusion is the beginning of loosening it. You are not your job. You are the person who does it, who chose it, who brings values and attention to it. The role is something you do, not the whole of what you are. Right now those feel like the same thing, but they are not. Start building one small part of your life that has nothing to do with work: a hobby, a friendship, a practice that is just yours. It does not have to be big. It just has to remind you that you exist as someone even when the job is set down.