What food 'rules' do you live by?

The picture above is one that I have on my desktop, and look at almost everyday.  It is a picture that I really like, and it reminds me more of an Arcimboldo, than a Van Dijck still-life.  This post is generated by Tricia's question on her blog today: "What food 'rules' do you live by"?
In case it has not been obvious, I have a slightly conflicted relationship with food.  I grew up in a vegetarian family, with my mum following the tenets of ayurvedic cooking.  It was even worse when we had family come and stay with us.  There were even stricter variations on this, and my mum ended up having to cook several separate meals, with separate utensils.  One of my cousins had lived in an ashram in India for a couple of years, and he did not eat garlic or onions as they are Tamasic foods, "provoking mental dullness". Going on holiday was an experience as my mother would take her own pots and pans with her - the same with cutlery.  We never ate out, as no restaurant could follow the strict dietary  principles and tenets my family adhered to.  Food was a necessity, a fuel rather than a luxury, and 'treats' were never food-related.  So what changed?
Well, I moved to Italy and discovered the Mediterranean diet.  When I used to tell people I was a vegetarian, they really struggled to come to understand what exactly that meant - after all, this was Italy in the 1980s, and vegetarianism had not yet become mainstream.  Being invited to people's homes was always dramatic, as people just did not know what to make for me, and always felt that I "hardly ate anything".  My parents however had always encouraged me to try new things and have an open mind, so I decided to try all these things I had never eaten - salami, proscuitto, carpaccio etc etc.  It was fine, and I enjoyed it all immediately, as being a vegetarian was never really about 'ethics', though I guess it is the basis of ayurveda anyway.  However, my family never banged on about that aspect, so I really was free to make that leap.
When I left Italy and went up to Oxford, I went back to being a vegetarian.  Then, when we moved to Geneva things were no longer so black and white - my perception of food as fuel had changed and food was also now a luxury.  In Italy one spent hours talking about food and wine which is such an integral part of la bella vita.  I could not just undo all that.  Living such a focussed life in Oxford made sticking to a vegetarian diet easy, but once back in the 'real' world, it was hard to get the jack back into the box.    Food is part of a cultural backdrop and it is quite hard to now think of it as strictly 'fuel'.  Let me also add that Stuart has been very good about all of this, and he enjoys the vegetarian diet.  He can take ayurvedic cooking in small doses, but like me prefers a wider variety of world vegetarian dishes.  My bible in the kitchen is Madhur Jaffrey's World Vegetarian Cookbook, but I vacillate wildly between Italian and Vegetarian cooking.  I just cannot choose.  In my mind I would like to go the vegetarian way, but how could I forget about all the other meat and fish-based dishes?
In addition, other issues have crept in: fast food and other stuff.  I had never eaten a McDonald's until I moved to Italy.  Firstly McDonald's did not exist in South Africa and secondly with all the ayurvedic goings-on, it was the furthest thing on my mind.  In Siena, there was 1 McDonald's in the whole town, and hardly anyone went there.  The only people who went there were the boys in the military because they had very little money to do anything else.  Mind you, a menu meal was about 6 Euros (about 8 USD).  Still, it quite a novelty to have it.  In Geneva, they send you free coupons in the post, so we used to wait for those to have a McDonald's.
But back to the original question in Tricia's post: What food 'rules' do you live  by?  I cook everything, we rarely eat out, pizza is a once a week treat.  McDonald's never happens.  I still struggle with crisps, chocolate, biscuits and nuts.  I try not to have them, because it is like opening the floodgates - once I start, it seems impossible to stop, so I just do not buy them.  The idea behind this is that if I want something, I am going to have to walk to the shops to get it.  Naturally, this plan does not always work, and some weeks I do buy stuff and think I can control it....   I have just had a quick chat with Stuart halfway through writing this post, and he has come up with a wonderful idea.
Stuart has suggested that I add another item to my 101 things: have a vegetarian week a month for 6 months, then have 2 vegetarian weeks for 6 months.  That will bring me (us) up to a year, and then I can decide what I want to do after that.  When friends come around we can still offer them meat etc, as I do not believe in foisting my choices upon others.  I love that idea of a vegetarian week a month, so watch this space for an update, and I love Stuart for being so supportive with my dilemmas!  So let me extend Tricia's question to everyone: What food 'rules' do you live by?