depression
"I used to have horrible nightmares, couldn't sleep sometimes because of visions in the dark, occasional sudden bouts of intense unjustified anger, etc.  I've been on Prozac more or less (I'm not great about taking the pills) for 10 years now.  I probably average 20 mg/day over time.  If I stop taking it for several weeks, I will notice the angry spells starting to come back, etc, and that's my cue that I need to start taking it again.  It has been very helpful for me.  It's not a cure all, and maybe the highs of life are not as frequent, but they still come.  And I'd rather have that and contentment than the awful lows.  No free rides, but I enjoy my friends, exercise, family, and relationships.  Overall, a Godsend for me."