1. You’re burning the midnight oil to finish a deadline.
Eat a light dinner. "When you eat too much, your body expends most of its energy on digestion so it has less to put towards concentration," says Rachel Begun, M.S., R.D., a spokesperson for the Academy of Nutrition and Dietetics. Skip—or limit—the carbs: they increase your body’s production of the sleep-promoting neurotransmitter serotonin, making you groggy. Instead, opt for a protein-packed meal, like grilled tuna over a bed of spinach.