The mind processes complex thoughts, making memories stick, clearing out brain waste and much more. Sleep retains neuroplasticity, giving the ability for brain cells to strengthen important connections, and get rid of less important ones which is still an active area of research. When you don’t sleep, it’s harder to control emotions and moods. Sleep helps maintain executive functioning skills making us moody, less irritable, and less likely to lash out. While the brain sleeps, harmful toxins are cleared out. Certain proteins accumulate in the brain over the course of the day while awake. Proteins get cleared out during sleep.