insomnia
"I have had insomnia, sometimes quite severe (couldn't sleep for 3-4 days, which is severe) and had been successfully taking 10mg of Ambien for the past 5 years, along with melatonin 5mg. Then it stopped working. I'd wake up after 2 hours of non-restful sleep. 
  My Dr and I decided taking a vacation from Ambien might be helpful. I had tried lunesta first, before Ambien, years ago...and dreaded the awful taste. 
   But hey, I have to sleep. 
   The first weeks surprised me. I didn't get dazed or feel weird before falling asleep, like with Ambien. I just slept 
   The downside is I wake achy and stay groggy, sleeping LONGER than I planned...so it is hard to get "up and at it." 
    I'll take the sleep, though. Adding melatonin help"