1. Being a couch potato: sitting in one position for long periods of time can sap your energy, even if you're watching the TV or using the computer. Your body equates the stillness with going to sleep.
Solution: stretch often, get up and walk around away from your desk or sofa. Frequent breaks will keep your body alert.
Read more about getting started with exercise.
2. Poor posture: a lot of your energy goes on keeping you upright. Bad posture - such as hunching forwards and slumping in your seat - puts your spine out of alignment. The more out of balance your spine is, the more your muscles have to work in order to compensate.
Solution: whether you're moving, sitting or standing still, your head should be lined up over your body - not sticking out in front of it -so your ears are directly over your shoulders.
Read more about how to improve your posture from the charity, BackCare.
3. Crash dieting: while it will boost your energy to lose excess weight, going on a crash diet isn't helpful. Very low calorie diets, especially ones that give you less than 850 calories a day, will make you feel even more tired and can damage your health in other ways.
Solution: lose weight by eating healthily, cutting out junk and sugary foods and reducing your portion size. Aim to lose no more than 2lbs a week.
Read more about how to lose weight sensibly.
4. Cabin fever: it's all to easy to become homebound, especially if you have a young child, you work from home or you've been driven indoors by the cold days and long, dark nights of winter. But lack of light and fresh air is a key cause of tiredness.
Solution: get out for a 10-minute walk at least once during the day or when you're most tired. Even if it's cloudy, you'll be exposed to more natural light than inside and you'll feel more alert. If you simply can't get out the door, a few minutes in a room filled with natural light may also help.
Read more about overcoming the winter blues.
5. Sugary breakfast cereals: sugary breakfasts, such as processed cereals, pastries, muffins and toast with sugary spreads, will give you a quick surge of energy as your blood sugar peaks. But your sugar levels will slump just as quickly a couple of hours later. The result? You crash as you run out of energy.
Solution: to get a steady release of energy all morning long, eat a breakfast that's based on unrefined starch. For example, home-made porridge with semi-skimmed milk and a little honey, or wholemeal cereal with fruit sliced over it, or an egg with wholewheat or granary toast. Try to choose breakfast cereals that are wholegrain and low in salt and sugar.
Read more about how to eat healthily.
6. Constant worrying: if you're fretting about something all day long, your heart rate and blood pressure rise, and your muscles tighten, leading to fatigue and aches.
Solution: set some time aside to concentrate on your worries. Try to think of positive solutions, then put the worries out of your mind. And schedule that dental appointment for first thing in the morning so you don't spend all day fretting about it.
Read some quick-fix tips to relieve stress.
7. Exercising too much: regular exercise is good for you, but working out intensively every day may not be good for your energy levels, especially if you're a beginner or trying to get back in shape.
Solution: take a day off between strenuous bouts of exercise. But beware of leaving more than two or three days between sessions or you might fall out of the habit.
Read more about starting off with exercise.