We all have our little vices — coffee to kick-start the day, a big glass of merlot to polish it off, and countless sneaky cigarette breaks in between… Even the most virtuous amongst us has a secret stash of chocolate and an unhealthy appetite for exercise. Exercise? Yip, too much of anything — even a good thing — is bad for you.

The key, as my mother is so fond of extolling, is moderation. "Everything in moderation". But moderation is a relative term, which if nudged gently can comfortably cover that extra glass of wine or pack of cigarettes. So, we've put together a guide that spells out exactly what moderation means when it comes to your vice of choice…

Alcohol

Contrary to popular belief, alcohol is not entirely bad for you. In fact, moderate consumption has been found to reduce the risk of coronary heart disease and strokes. That being said, excessive drinking can lead to cirrhosis and brain damage, not to mention countless fatal accidents and acts of violence.

Although some regard it as conservative, the guide provided by both the US and UK governments is one drink per day for women and two for men. The discrepancy stems from variations in body mass and the fact that women have less alcohol dehydrogenase (the enzyme that breaks down alcohol in the stomach) than men.

And no, you can't stock pile your alcohol credits — abstaining for two weeks does not justify a weekend binge!

Unfortunately, if you are being 'moderate' about your drinking, the measure of a 'drink' is pretty inflexible — you can have 350ml of standard beer, 145ml of wine or 44ml of distilled spirits.

Caffeine

A lesser evil, caffeine isn't likely to result in death (it would take about 100 cups of coffee in one sitting) or even permanent damage, but consuming too much will leave you feeling restless, irritable and nauseous or suffering from a headache, muscle aches, disorientated thoughts, heart tremors and insomnia.

Mmm… perhaps that mid-afternoon pick-me-up is not really that necessary.

However, the good news is that it takes about 500mg of caffeine before your body goes totally out of whack, which means that you can comfortably get away with two to three cups of filter coffee a day.

There are a number of factors which increase your body's sensitivity to caffeine including body mass and stress levels (heightened stress increases sensitivity). Your body doesn't store caffeine, but it does take a number of hours to eliminate the stimulant and its effects. If you decide to cut out caffeine completely, you may notice some temporary withdrawal symptoms such as headaches, fatigue and irritability.

Caffeine in moderation means keeping your daily intake to between 200mg and 300mg. Here is a rough guide to help you keep tabs on your caffeine consumption.

Cigarettes

Unfortunately, the moderation law does not apply to smoking. It's poisonous. Period. Recent studies by the American Cancer Society have found that smoking as little as one to four cigarettes a day makes you almost three times as likely to die as a result of coronary artery diseases and it also increase your chances of dying from lung cancer by three if you are male and by five if you are female.

Every time you take a drag on that ciggie you are filling your body with carcinogenic chemicals that will undoubtedly lead to cancer, emphysema and all things horrid. There really is no way around this one. Smoking is bad for you, all the time, in any quantity.

Exercise

While most of us suffer from a lack of motivation when it comes to hitting the gym, there are some who are a little too motivated. Exercise, like smoking or drinking, can become an addiction — an endorphin-fuelled form of stress release or an out-of-control attempt to lose weight.

Unlike other vices or addictions, there are no hard and fast rules about how much exercise is enough, but there are signs that you are training too hard. If you are exercising regularly and suffer from insomnia, muscle fatigue, headaches, an increased susceptibility to colds and flu and a decrease in performance or stamina, you may be over-training.

Another easy indicator is your attitude to exercise — if you are letting your desire to exercise interfere with your job or relationships, if you struggle to take a day off even when you are sick and are getting little joy out of your training, then it is probably time to slow down.

If you suspect that you are a Duracell bunny in the making, it is probably a good idea to make sure that you take at least one day off a week; alternate hard and easy training days; and follow a programme that is filled with variety.

So, there you have it. You need not be racked with guilt every time you indulge in your favourite vice… Unless of course your vice comes in packs of 20, in which case it's probably time to whip out those nicotine patches.