narcolepsy
"I'm surprised by the majority of people's reactions to Nuvigil (though, it's the only medication I've tried so far). Before starting up with the medication I was exhausted to the point of feeling sick most of the time. After starting the medication it's like night and day, I typically feel great. Some days are better than others, and I never feel 100%, but it's the best I've felt in years and it hasn't fluctuated in two months I've been taking it."