For me, I find that I do need some structure.
I did a very strict diet a few years ago, lost 5stone in total and kept it off for 4 years, and put it all back on in one really stressful year. I since had tried to go back on it, but I'm in a different place now, and my found it difficult being very strict whilst 1. dishing up my girls loads of lovely food, 2. trying not to eat their leftovers after they turn their noses up at their lovely food, and 3. trying not to be obviously dieting strictly so as not to bring them up thinking it was the norm. All-in-all I couldn't hack it.
So, after reading the two books I mentioned before, I've decided to implement some structure, and it seems to be working for me. I weigh myself every day (same time, without clothes), so I get used to my body's normal fluctuations. If I have put on more than I was expecting, I'll be more conscious about what I eat the next day or two, without punishing myself by being ridiculously strict. I'm using MyFitnessPal to record what I'm eating, again, knowledge is power. I've bought myself (and was given some I asked for for Christmas) some excellent low calorie cookbooks, and aim each meal to be around (or less) 500kcals per portion. As I said, I am portioning food out properly, so every meal I dish up all the food, and put it straight in the freezer when cooled if there is extra, so that I don't eat it needlessly as I would have done previously. And I am not limiting the fruit or veg I am eating, but having as much as I want: with meals I'm aiming for half my plate to be veg, and I can have as many fruit/veg snacks as I want during the day.
Like others have said, I'm in this for the long-haul and so far touch wood it is working for me. Whether what I'm doing is called a 'diet' or a 'life style change' I don't really care, but I'm hoping to train myself healthy eating habits so that eventually they'll come naturally to me.