One Man's Taxonomy of Dreams

1)  There is a goal that you are required to reach, but your path is littered with obstacles; it's clearly futile.  (Ex.  You must find the dormitory room that the college has assigned to you.)

2)  A pleasant and comforting dream, but on awakening you realize that that train has left the station.  (Ex.  A young woman from long ago slips beneath the covers with you, a young man from long ago.)

3)  You bear witness to the early stages of an apocalypse, with throngs of people running and holding their hands in the air, but your feet are frozen to the ground, out of both fear and infirmity.  You awaken grateful that the apocalypse has not yet come.

4)  Bandits lie in wait for you, but it's a lucid dream; you know that you are dreaming; you check out of it before you are blown away.  Moreover, it being only a dream, you are not that scared even in the midst of it.