Chances are your carefully thought through new year’s resolutions will now be no more than a distant memory. Fear not, redemption is at hand. February 21 marks the first day of Lent and a perfect opportunity to go through the whole soul-destroying exercise once more.

But instead of trying and failing to stick to your guns, there are techniques available to make sure this time is different. The first golden rule is to be realistic about what you are hoping to achieve. Unlike the New Year, which stretches out indefinitely, Lent is just 40 days, so this is already a more manageable time-slot in which to be good.

The trick is not to try to give up everything at once. If you starve yourself while simultaneously ending your 40-a-day smoking habit, you could morph into the Incredible Hulk every time someone makes you angry (ripped shorts included).

Instead, choose one vice you want to tackle. In January, I made the dubious decision to go on a detox that would only involve drinking a syrupy-lemon sludge (www.lemondetox.com). No food, no other drinks - just the sludge.

Aware that I like my food and have the sticking power of Teflon, I decided to give it a go for just five of the recommended 10 days. This felt like a more manageable goal, but I still struggled to get through headaches, grumpiness, light-headedness and severe food cravings.

Despite all this, I would have got away with it but for going into that pesky school on day five. There, in the school canteen, my resolve melted in the face of sausage, mashed potato and a chocolate flapjack. School food had never tasted so good.

What I learnt was: resolutions are harder to keep in schools than offices.

With so much temptation around, busy teachers need a great deal of energy and willpower to keep them going throughout the day. They must, therefore, be even more realistic about what they can achieve. Trust me, crash diets don’t work. Having lost 4lb over four-and-a-half days, I promptly put 5 back on - and feel all the better for it.

Apparently this is backed up by medical science. The human body can only burn 2lbs of fat a week, so any more than that must be in the form of water, muscle or organ-tissue loss. More moderate weight loss, I learnt far too late, is much more likely to stay off because it does not involve chronic dehydration or becoming weak and puny. Those who break their goal into small manageable chunks are much more likely to succeed.

Eating five portions of fruit and veg a day, for instance, can seem daunting, but less so if you swap your lunchtime sandwich for a salad once a week. Alternatively, eat an apple before reaching for the biscuit tin - there are 74 calories in a digestive biscuit and about 50 in an apple, but the apple is a lot more filling.

Other small changes can have an enormous effect. Just by swapping full-fat milk for skimmed, you can cut out approximately 100 calories per cup of coffee while hardly noticing the difference. If you want to cut down on alcohol, instead of feeling guilty every time you reach for the bottle, simply vow not to drink two nights running.

If exercise is your thing, make sure you take the stairs instead of the escalator, or swap one nightin the pub each week for an evening at the gym.

Rome wasn’t built in a day and your new, improved self certainly won’t be either. But by taking your time and being prepared, you can get there eventually - and feel terribly virtuous in the process

YOUR SURVIVAL GUIDE

* Draw up a plan of action. Be realistic about what you can achieve.

* Keep busy to help take your mind off whatever you are giving up.

* Drink plenty of fluids.

* Get active. Exercise helps you relax and can boost your morale.

* Think positively. You may become irritable but this should pass after a couple of weeks.

* Change your routine. Try to avoid the usual triggers, such as a shop where you buy cigarettes or chocolates. Instead, do something entirely different with your free time.

* No excuses. Don’t let a crisis or good news destroy your willpower.

* Reward yourself with treats to keep your motivation levels up.

* Try not to snack on fatty foods.

* Take one day at a time.