Tom, I am not an expert at this, in fact I struggle with conditioning myself. I think the first thing to do is to recognize that it is conditioning (you've done this! congrats!). The next thing to do is to remind yourself, as you go into the situation, that you are experiencing pain only because you expect to.
If it's at all possible, you might try doing whatever it is that you've become conditioned to for a very brief amount of time, telling yourself it's TMS all the time. Then build up slowly as you become deconditioned.
I was noticing that my foot pain got worse every day during 5th period. There was no reason for this except conditioning. Since I have to teach 45 minutes, I could not use my building-up strategy. However, last week my 5th period class met in a computer lab instead of our regular classroom. I was on my feet more than usual, walking around and checking students' work. However, I noticed that I had less pain than usual during the period. (It made me wonder if subconsciously I was actually conditioned by the room in which my 5th pd. class usually meets.) This helped break the conditioning a great deal--I've noticed it's much less during 5th period this week.
I hope this helps!
Gail