More often than not, we are awakened at least once a night: we can't keep ourselves from waking, but we can help ourselves to go back to sleep.
Go Back to Sleep
Keep a notebook and pen on your bedside table. Begin writing to-dos and reminders an hour before bed so that you aren't compiling a mental list for the next day. If you awake suddenly remembering an important task, write it down rather than trying to commit it to memory.
Try counting backwards from 300 by 3s. Simple math can keep our thoughts from wondering and yet isn't so difficult that it will frustrate you.
If you're still awake after 15 minutes, get up and do something quiet, like reading a book. You have to let your body and mind slow down to be able to slip into sleep - so that means quiet activities only.
Sleep involves several stages: REM sleep is accompanied by vivid dreams and memory consolidation; the third and fourth stages of sleep are deep and restorative. Each night you cycle through these stages. When you hit the snooze button, you alternate between wakefulness and light sleep, which might feel comforting - but there is no physical or mental benefit from this.
You Snooze, You Lose
One surefire way to fight your fatigue is to ban the snooze button. You've decided what time you are going to get up every day - and that does not mean 15 minutes early and snoozing until it's time to get out of bed.