I totally get this. For a long time when I was the sole on-call sysadmin at my old job and we were going through a particularly bad period with a lot of technical challenges, I would get a knot in my stomach every single time my phone rang. Not just metaphorically -- I had acute physical responses to the sound of it. Not only that, but the feeling of relief when I looked to see it wasn't a work call was palpable as well.

Because my anxiety was very narrowly focused, I eventually solved this problem by getting a phone that allowed me to assign custom ringtones,and setting up a "work" ringtone separate to personal calls, but I still totally understand what you mean.