Hi Chriscpaul, welcome to CWE!
My first grand mal seizure arrived out of the blue when I was 35 -- I sympathize. I know they are hard on the system. It can feel like you've been run over by a truck! I imagine that as a firefighter you are in pretty good shape, so that should help with your overall recovery. It takes time, but the body is amazingly resilient.
Unfortunately, there are no guarantees about repeat seizures, just statistics: About 2% of adults have a seizure at some time during their life. Two thirds of these people never have another one -- hopefully that number includes you.
If you have no no precipitating head trauma, no prior history of any seizure-like activity, and if the circumstances of your seizure (dehydration/fatigue/caffeine) were a freak occurrence unlikely to happen again, then there's a good chance it's a one-off. If you can make it to the 6-month deadline seizure-free that's another excellent sign that you will remain seizure-free in the future. Was an EEG done at the time of your seizure? And if so, did it come up negative? That's yet another hopeful sign. I assume your neurologists were aware of all the factors, and took you off the Keppra because they felt reasonable sure that you would remain seizure-free.
Despite this, it is very normal to live in fear of having another seizure. It's a traumatic event. Your memory is zapped and your body takes a beating. But the longer you go seizure-free the more likely it is that your anxiety will recede. In the meantime, it may help your peace of mind to be very proactive about your general health. Listen to your body -- moderate your intake of caffeine, avoid fatigue and stress, make sure you are eating and drinking properly, and make sure to relax and enjoy life.
Best,
Nakamova