They are the mantras of every health and fitness book. 'It's all about diet and exercise', 'Eat less, do more', 'Calories in, calories out', 'No pain, No gain' - but there's something missing. I am talking about the third, and critical factor, rest.

Rest is everything from allowing yourself a good nights sleep and doing things you enjoy, to taking a bit of time for yourself everyday.

In our modern lives there is a social stigma attached to taking rest. People brag about their hectic schedules, their all-night work benders that justify a quadruple espresso come morning. We see rest as failure, but it's a fact of life - if you want to be happy, sometimes you just need to take some time for yourself. This time should be embraced, not criticised.

Not many people are aware but, exercise is a stress on the body. After exercise, you are less fit than when you began. Its only through adequate nutrition and plenty of rest that your body uses that stress to build something better. Without this rest you run yourself down. This is true in all aspects of life, this chronic stress (including too much exercise) can increase inflammation in the body.

The Chinese view of Yin and Yang explains this concept well. You have things that take it out of you such as work, money worries and exercise to name just a few, and things that bring it back such as a good nights sleep, cooking homemade food and taking a few minutes out of each day to read this blog. These things nourish your body. A simple expression might be that every time you work 'out', make sure you work 'in'.

If you wake up and that gym class seems too hard, it's ok! Your body is trying to tell you that the balance isn't right. A useful tip is the 2% rule. If you feel you cannot improve on your previous gym session by 2%, give it a miss. Exercising whilst exhausted is a sure fire way to get injured and lose motivation.

Sometimes, when everything except for your moodscope score seems too much, just remember life is a balance. Take some time out, treat yourself and get some rest.