I think a good proxy for what you should and should not be eating is how much you enjoy the food. If you really enjoy it a lot, then it is easy to over do it.

I think a good proxy for what you should and should not be eating is how much you enjoy the food. If you really enjoy it a lot, then it is easy to over do it. However if it is mostly palatable, but doesn't give you that feeling of bliss (compare salad without dressing vs. pizza or chocolate cake), then you won't be necessarily going back for seconds/thirds once full. Of course, this can be mitigated if the food has a negative feedback cycle. I'm that way with shellfish, after a certain amount it becomes nasty tasting. Same with a good steak, after I've eaten enough I can't imagine shoving more down. But with pizza, I always go back for that second or third slice.