Beware of your current emotional state before watching this film... believe me if you're not in great shape and then happen to watch this movie... probably you'll kill yourself after :( Of course that's hyperbole :P
Seriously, this is a practical example of a film that will depress you... A story of a respected businessman(played by Kevin Costner) even awarded as "Man of the Year"; a passionate husband; a loving father - but an addict who cannot escape from his alter ego urging him to kill... yes he's addicted to killing...
While watching this kind of film you may be physically relax, but after that watching you'll be emotionally restless...
Include the following in my "No no" list:
Into the Wild(2007) Emile Hirsh - for the gloomy ending of the story
Wicker Man(2006) Nicholas Cage - for the morbid experiences and sufferings of Edward :( plus the terrible ending
300(2006) Gerard Butler - only for the barbaric killings but other than that the film is excellent... AHOO! AHOO!