The Non-Existent Fifth Person

I am a polar explorer. Trapped by a blizzard, my three other teammates and I are stuck in an abandoned polar observatory. There is no power here, and our reserve fuel has run out. To survive the extreme cold of -50 degrees, the four of us decided to use the "circular sleep method": Each of the four of us lies in one of the four corners of a square room. Every hour, the awake person walks along the wall to the next corner, wakes up the next person, then lies down to sleep there themselves. The newly woken person then walks to the next corner, and so on, ensuring there is always someone awake to monitor the environment. I was woken three times like this, half asleep and half awake. But when I was woken the fourth time, I did not walk to the next corner. Instead, I ran madly out into the blizzard outside and killed myself. What happened?