First try to figure out why you are not falling asleep. I used to work overnights and slept during the day. I averaged about 5-6 hours a day and felt fine. Unfortunately I wasn't. The problem was exacerbated when I moved to a new apartment and changed beds. I slept even less which eventually led to more problems.

Lack of sleep can do more than affect your health. It affects how you think, process information, and behave. Because changes happen subtly you may not be aware they are taking place.