REUTERS/Mike Segar
Sheryl Sandberg, Facebook's Chief Operating Officer.
That's because the very last thing you do before bed affects your mood and energy level the following day, since it often determines how well and how much you sleep.
Knowing that, we decided to find out how the most successful spend their nights before surrendering to sleep.
Turns out some - like President Obama and writer Michael Lewis - are night owls, preferring to work while the rest of the world sleeps; while others -like Arianna Huffington and Sheryl Sandberg - know how important sleep is, and force themselves to cool down.