Feeling tired all the time is becoming one of our most common ailments, and it can be the most frustrating as well. Even if you live a fairly sensible lifestyle and don’t have any serious health problems, you may still find yourself weighed down with constant fatigue.

"A lot of people confuse fatigue with sleepiness—it’s not the same thing," says Doug Cook, a registered dietitian and nutritionist at St. Michael’s Hospital in Toronto. Sometimes a viral or bacterial trigger, or other serious illness is the culprit. But fortunately, most of the time there are simple causes that can easily be fixed. "A lot of it is just lifestyle related," he says. "I think fatigue really is a symptom of the way society is: too busy, burning the candle at both ends. It’s has though what used to be confined to university students as become the norm for all stages of life."

Here are some common reasons that you might be feeling a lack of a spring in your step and what you can do to feel more energized.