The hours of sleep I do not sleep very well. Because we want to relax the whole body and brain. Late to bed can cause lack sleep. Time / work. Drowsiness, it may be more a hurdle.
To go to bed late, in a hurry. "so much of our body and brain need rest. To sleep late at night will cause insufficient relaxation. Time study/work, possibly as much drowsiness difficulty.
The sensitivity to go to bed, do not hurry to sleep late because both body and brain, we would like to rest, of the late will result in a vacation is not enough time to learn/work, it might be a symptom of a barrier sleepy.