This time of year, every year I do a detox. I use the term detox loosely as I feel it's more a re-evaluation of the food and drink being consumed rather than some fashionable diet based on special pills or shakes. I went on a Tony Robbins personal development weekend about six years ago and learned the idea there, and have been implementing it twice a year ever since.
In a nutshell, it's no meat, dairy, caffeine, fried food, artificial sugars, alcohol and nicotine for anywhere between 10 and 20 days. In addition, over the course of the programme you're meant to do a minimum of 15 minutes cardio on at least 6 occasions. On top of that, you're supposed to avoid combining proteins with carbs and to have something like three-quarters of your meals based on fruit or veg - neither which I particularly adhere to as strictly these days. Finally, don't forget to have lots of water.
This detox is part of my calendar and friends and family have got used to it all. The first few times were definitely quite hard, as my diet was in hindsight pretty shocking back then and disciplining myself felt like a chore. But I realised even then that the body needs a rest from the toxins once and a while. The weight loss and the extra energy I found was quite dramatic, particularly as it took a while for me to want to fully go back to my old ways anyway.
My lifestyle has evolved - I drink less, don't smoke (well, rarely), hardly eat dairy, still have a sweet tooth but am more sensible, and generally eat more fruit and vegetables. I even have "no meat Mondays". Something that started out as a bit of an experiment has become part of me. I'm not perfect at it, and I know when I do fall off the wagon it can be with a mighty thud, but overall I think the process is adding more value to my life than taking away.