Mental hunger is legitimate hunger. If I'm thinking about food, and want food, and I'm wondering if I should have food, and food, food, food, food, it's because I NEED it, not because I'm crazy or mistaken. Once I'm adequately fed, those thoughts go completely away.
For a long time, I tried to wait until I was stomach growling hungry to eat, but I now realize that thinking about food is a sign of hunger. It's the first sign you get. If you're not hungry, you're not thinking about it. Like peeing. LOL You don't think about it unless you have to go. Then it's all you can think about.
As far as continuing to eat out of habit, or not wanting to stop because it's so good, what I've found the most helpful is knowing I can always have more. I'll stop eating for now, but if I'm still thinking about food in 20 minutes, I'll have some more until I'm satisfied. The fascinating thing is that once I've had enough, I don't want anymore. Stopping eating is no problem at all. When I thought this was such a huge issue, it was because I was hungry. Go figure.