I have always tried to get as much as 8. hours of sleep for I know the subtle side effects of sleep deprivation. These subtle effects cause huge damages. Sleep deprivation is the reason behind most accidents between midnight and 4 AM.
For those with less awareness and didn't know about this, here are some symptoms of sleep deprivation.
1. Lack of coordination between the brain and the organs. This manifests as biting of tongue when eating, tripping while walking etc.
2. Increased frequency of déjà vu. Déjà vu is nothing more than minor malfunction of the brain. With sleep deprivation the frequency of déjà vu experience increases. If you felt like a psychic, get over it. It is just an effect of less sleep.
3. Black outs. As an event happens, the brain switches off for a fraction of a second to process inputs from sensory organs. This results in an experience like watching a movie from a scratched DVD.
4. Signs of OCD - obsessive compulsive disorders like doubting if you locked the door, switched off lights etc. This is because, the brain may not have registered the action due to some kind of black outs mentioned above. To compensate for this state, the mechanism to doubt and question kicks in.