A lot of unexplained anxiety can be chemical. My stepmother started having bad panic attacks as she got senile which I imagine was her brain and meds doing a number on her. If anxiety could always be explained, it could probably be solved but meds and therapy haven't managed to get rid of it.

I do evaluate the "threat" to me when I'm anxious and just "ignore" the ugly feelings until they go away if I don't see anything conscious and can't even "imagine" something (like the person I'm with is anxious and that's wiping off on me which can happen). It's been shown that some of the "wallflowers" at dances don't get picked because they're signalling their anxiety over being picked and in fact, pushing people away rather than "inviting" them to them. Anxiety is highly contagious.