Count sheep
Definition 1 of 1
Pro Tip 1/3Relaxing Imagery
The phrase evokes a calm, monotonous activity meant to induce sleep by picturing a repetitive motion. 
When she couldn't sleep, she tried to count sheep, imagining them hopping one by one.
Pro Tip 2/3Not Literal
Counting sheep is not a literal action but a mental exercise for relaxation and sleep. 
You don't really count sheep, just picture them in your mind as you try to fall asleep.
Pro Tip 3/3Cultural Classic
The idea of counting sheep is widely recognized in English-speaking cultures as a common sleep aid. 
He joked that he got so bored at work, he might as well have been counting sheep.