How do some people do it?

How do some people make it through the day with little sleep, I'm talking about 4 hours of sleep here and there. I know I need at least 7-8 hours to function. I have a co worker that texted me around 11:30pm and has to wake up at 4am. I know when I don't get enough sleep I feel so tired and grumpy

How do some people do it?
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