This is a fascinating read and Hat has put some fantastic stuff out there. I would like to weigh in with my own brand of support and experience in these things.
You are right insomuch that there is a catch 22 as to when to accept exposure and when not to. But Hat is right. If you are really feeling the pull of anxiety, then it is not the right time. This often happens during withdrawal. Exposures must be faced, but from a position of strength, otherwise you will go into a situation and almost will the negative response which in turn will result in the conditioned response that Hat mentioned.
The bottom line is that you need to believe that what is happening to you is just a symptom, like a sore throat in a cold. When you have a sore throat, you don't panic when you are talking - although you might reduce the conversational time to aid healing, but you KNOW it will pass. It is very difficult with the brain as it tries to reason and understand what is happening. But observing it from outside, you need to understand that the brain is just an organ like anything else and subject to ailments that will also heal in time.
I have been there. I couldn't even fill up with gas at one point for fear of queuing. I would time the fuel filling so I would be able to go right in, pay the cashier and walk out. I was not ready, but these were thing I had to do. This is where you start. You start to reason with yourself. What is the worst that can happen? Has anything bad happened before? It's been fine every time. But you need to break that connection. I started to realise that this was just a thought. I would start to tell myself to "bring it on" and "do your worst".
What you resist persists - the opposite is true.
It is all about letting go in these situations. It sure isn't easy, but I followed the work of Dr Claire Weeks. Her work, combined with my weekly therapy, got me out of my symptomatic head and back to where I should be. Just let your head shout as loud as it wants. Let it be. You will soon realise that there is nothing to come from it. But you have got to be in a place to start accepting that this is the case. If you attempt this without believing (or knowing) that this is truly the case, it won't work.
This is all I would append to what Hat has already very well described. He has always been the scientific part to my more holistic and therapeutic theory. Always a good combo!!
Wishing you a good Sunday my friend