maybe it's just that you're craving freedom.. [:))]
or wishing to experience the thrill of jumping!! remind yourself that riding an amusement park ride will have the same effect as jumping off a building tho (do you know the mega drop ride? it's fun [:))]) oh man i wanna go to disney world... :D:D (sorry this is off topic...)

I know what you mean by this. Though it very well may be a subconscious desire to commit suicide, I believe it may be also a mixture of an impulsive personality combined with boredom. Whatever you do, ignore these impulses! I definitely think it's something to talk to a real doctor about, for the very obvious reason that you're in danger because of it.