Why do we sleep and what happens while we sleep? Sleep helps our brain become stronger. While we sleep our brain sorts what we learned during the day. This helps us better remember what we learned during the day. During sleep our brain is busy moving events from short- to long-term memory. This helps our brain work more smoothly. This also makes it easier for us to remember. If we don't get enough sleep our brain is not able complete this work. Getting enough sleep helps us be our best!