Recently i have been able to finally stabilize a couple dreams which was quite a task for me as it's easy to get lucid but hard to keep. so in 2 or 3 of these somewhat stabilized dreams (im not sure if they were fully stabilized) i have had as the title says abrupt awakening such as:

1) im in my room i try and stabilize it works so i proceed to jump out my window before i can i hear a *THUD* and im awake (I did RC's)

2). im in a store stabilize once more and i look around seeing what kind of things they have. i turn my direction to the ground i see a little stool it almost teleports two inces closer i think oh-crap (still don't know why) and BAM awake!

So why does this happen is my REM time over or am i doing something wrong?