I've had experience with that. I hosted, spoke at and answered questions to a conference of over 200 health management workers and government ministers. I would say that the apprehension was actually worse than the event, as is mostly the case.
I know what you mean about feeling as though you are fine, then a panic attack coming along to set you back.
One of the members on here once said that you have to treat panic disorder like diabetes. Too much sugar for diabetics will cause problems, and to some extent, stress or pressure is our sugar.
But the fallacy in the metaphor is that I don't believe you have to worry about your panic on a day to day basis.
You have to truly believe that you will get over your panic for good. And the only way I know how to do that, is stop fearing them.
When you've been through one 'spell' of panic - you know what to expect. You learned and coped and built techniques to work on it - so there's nothing to fear.
If it comes again - it will be nothing like the first time. Because you've built up resistance. Not immunity, but resistance.