Ever have one of those dragging days? The Happiness Project suggests you can get an instant short-term energy boost simply by going outside:
Go outside into the sunlight; light deprivation is one reason that people feel tired. Research suggests that light stimulates brain chemicals that improve mood. For an extra boost, get your sunlight first thing in the morning.
This is especially important for those of us who spend our workdays behind a computer screen; natural light not only can energise you, but it also saves your eyeballs from getting too tired.