After a long, exhausting workday, exercising sounds like the last thing you'd want to do, but getting your sweat on will actually energize you. Fatigue along with mood and depression improved after a single 30-minute moderate intensity exercise session, according to a study published in Medicine and Science in Sports and Exercise. "Everything we do uses oxygen, so when you exercise it helps you work more efficiently and you don't tire as easily," says Nutting. "You also function better mentally."