Businesspeople may think they are getting enough sleep when in reality their minds have gotten used to the new baseline of chronic tiredness, meaning they are not in as good shape as they’d like to believe, reports Entrepreneur.

Entrepreneurs and busy professionals tend to burn the candle at both ends, which often means regularly cutting back on sleep or subsisting on the bare minimum. Many prominent businesspeople like Donald Trump and Martha Stewart brag about getting by on as little as four hours a night to stay on top of their empires.

The modern work culture tends to promote the idea that sleeping is time wasted and that as long as people feel OK, they’re probably getting enough rest. But is how you feel really an accurate gauge of how well rested you are?