When you sleep, your brain literally recharges, removing toxic proteins that accumulate during the day as byproducts of normal neuronal activity. This ensures that you wake up alert and clear-headed. Your energy, attention, and memory are all reduced when you don’t get enough quality sleep. Sleep deprivation also raises stress hormone levels on its own, even without a stressor present. Happy people make sleep a priority, because it makes them feel great and they know how lousy they feel when they’re sleep deprived.