I know what you are saying as it has happened to me, unfortunately there is no off switch and looking for one can actually make it worse. The ones that appear to turn it off are the ones who lose the Fear of the thoughts and feelings. Once the Fear is lost the thoughts and feelings no longer matter.
Treat all the symtoms the same and that is just a symptom of Anxiety, nothing more. Its just your body being tricked by very sensitised nerves.
Try and stay in the moment and what I mean by that is when you do get the thought or feeling that seems to trigger your anxiety try not to add to it by imagining what you think will happen, just let the thought or feeling be there.
Know that you may well feel anxious as the time gets closer, but that you will be ok. You probably know by now that avoidance isnt an answer but facing it is even if this means having to use medication at first.
Claire Weekes is a good read for Anxiety. Self Help for your Nerves is one of her books. CBT for panic is also very good, there is a link on this site.
http://www.nomorepanic.co.uk/showthr...ight=cbt4panic