Your brain works like a dishwasher when you sleep, cleaning out the dirty information and tidying up the important stuff. You can also think of the sleeping mind as working as a garden, growing “synaptic connections between neurons” so neurotransmitters can pass through.
“Your brain cleans itself out when you sleep—your brain cells shrinking by up to 60% to create space for your glial gardeners to come in take away the waste and prune the synapses.”
Sleeping permits the glial gardeners, also called “microglial cells,” to sweep through your brain and make space for learning new information. A well-rested brain is like walking gracefully through the park. On the other hand, a tired brain leaves it cloudy.
“Thinking with a sleep-deprived brain is like hacking your way through a dense jungle with a machete. Its overgrown, slow going, exhausting.”
The brain also recycles synaptic connections during sleep. Thinking about positive things throughout the day will help keep those thoughts top of mind. Meanwhile, harping on jealousy or hatred will make the brain cling to unwanted trash.
“To take advantage of your brain’s natural gardening system, simply think about the things that are important to you. Your gardeners will strengthen those connections and prune the ones that you care about less. It's how you help the garden of your brain flower.”
You are what you think about all day, which gets reinforced during sleep. Be mindful of the memories you want to keep and forget the rest, letting the brain delete the crap.