its because u have an erratic sleeping routine, streamline it...
for example, for one day (preferably the weekend when u have no work) do not sleep in the afternoon... u will feel tired earlier at night and try to sleep latest by 11pm.
quit smoking, drinking tea or any caffeine derivatives (coffee, coca cola, mountain dew, red bull) in the day time. a cup of tea early in the morning does no harm, and actually keeps u fresh the whole day..
if u have any tensions or anxiety (which almost everyone has these days), talk about it with a close friend/ family member.. when u "talk ur tensions out" u r very relieved and the other person always advises u in a positive way and can thus solve ur problems.
and pray... it helps a lot...it keeps u fresh the whole day and gives u peace at night...