Long Period Downloading Troubles.

[4D85]

So I am downloading a large file right now (around 50 gigs), and I will leave Bittorrent alone overnight (computer is still on, doesn't hibernate automatically), and when I get on in the morning Bittorrent is exited out of and hasn't downloaded anything. Does this when I go to school too. The only way to make sure that the file is being downloaded is to stay on the computer and then it will work. Checked the auto shutdown settings and AutoShutdown is disabled. So I just don't understand why It still won't work when I leave it alone for a long period of time. NOTICE: It works when I am on the computer constantly (like when I play a game or browse youtube), only when I leave it alone for a long period of time that is over about 2+ hours it will turn off.