My eating is pretty much based on a penalties and rewards scheme. My daily limit is about 1800 calories, which allows me to eat a fair amount, but not so much that I lose control of my weight. What I eat in those 1800 (or fewer) calories is up to me. I'm not on a particular diet, but I have found that what I want to eat tends to be fairly healthy. And that is where the penalties and rewards come in. That slice of chocolate cake is massively calorific, but it also hugely delicious. So, for me, the reward outweighs the penalty. Conversely, a packet of crisps, for example, doesn't do it for me. The taste (the reward) is, for me, not that good, so the penalty (the calories) outweighs any possible benefit.