 Deeper sleep, deepest sleep, and REM, or slow-wave sleep. That's the stage where you're most likely to wake up. And if you tend to go to bed at roughly the same time on a nightly basis, these cycles are roughly the same length, and you may wake up at the same time in the night. Now, remember this as a general rule. You sleep more deeply in the first half of the night, so you're more likely to wake up during the second half of the night. And yes, most people do tend to sleep a little lighter