Sometimes it isn’t how much sleep you got that’s important, but how much sleep you think you got.
Our own perception of how much we slept during a night can be startlingly inaccurate. Dr Allison Harvey (now of UC Berkley) took insomniacs and measured how much they actually slept during the night. Despite the insomniacs reporting that they had only slept for two or three hours, they had in fact been asleep for an average of 7 hours – only 35 minutes less than a control group who didn’t have any problems sleeping.