HI Stacie
Alex and I also experienced an unexpected "anti-climax" when told we were all clear...

I can only suggest that if you consciously push your fears aside and replace them with "what can I do today to make this day count" or some other thing that works for you, it will eventually become habit - and one day you will wake up and realise you have gone a whole day without worrying about it, then two, then a week and then a month and so on.

I guess my point is that what you are feeling is normal but you should do everything you can to keep it in the background and not let it rule your day.