I think I understand what you're saying
@Abstract - my perceptions of threat are almost always of an interpersonal nature versus a physical one. Discerning real and perceived threats is a hard one for me too because I used to always be on the look out for threats, and saw them when they probably weren't there. In my life, so many times, I remember being all worked up about someone being against me, only to learn that that the person wasn't. For example, I quit a job one time in a huff because I was convinced that the boss was unhappy with me, and felt that everyone thought I was not good enough. I felt a critical gaze all the time and I finally couldn't take it any more. When I told the boss I was leaving, he pointed to his assistant and asked, 'it was because of her, wasn't it?' (The assistant boss was kind of blunt to people). It hit me like a bucket of cold water the realization that all the negativity I was perceiving was all "in my head." To my shame, I let him blame her because I had no way of explaining what my real reason was. But no matter how many times I get that reality check, I can still create phantom threats that seem absolutely real.
I think just doing the work of healing has naturally helped ease my HV. But earlier on in my journey, I remember one thought that I learned from a therapist that helped me to begin to put distance between my perception of threat and reality. If my perceptions were running away from me, I would ask myself, 'would you do that'? Can you imagine him/her doing that to someone else? Often, I could not imagine doing that bad thing I was perceiving or that person I was fearing doing it. For example, if I was feeling paranoid that a colleague was trying to undermine me, I would think really hard about whether I could imagine her doing that to someone else. If she is a decent human being, usually it's very clear that they would never do that thing you're worried about. But I do have a colleague who does sabotage people, etc. So I knew that some of the things she did was real and not merely perceived.
Also, from reading (I forget which book), I picked up on the fact that if I'm thinking in terms of "they", it is almost 100% the case that it is merely perceived. There is no "they". A group of people do not act in coordination (usually) to "get" you, at least after high school age. The 'they' is just a construct that serves to voice the threat.
I hope I made some kind of sense.