But what time should you go to bed to make sure you sleep well throughout the night? Enter the time you’d like to wake up in our tool below and, based on 90-minute sleep cycles, we can tell you ...

So for example, you still wake up at 4:30 in the morning, to go workout, what was it about your time in the Seals, that you wanted to keep these habits up? Jocko Willink: They're good habits ...

Aim to get to bed early enough so you wake up feeling refreshed. Stick to your sleep schedule every day, including on your days off. Your body will begin waking up at this time naturally.