I confess, I eat too much. So I'm not often in that situation. (But since my weight's stable and within 5# of what I'd like it to be, I don't stress about it too much.)

I don't eat fast food. And I don't do well with anything frozen, so melting ice cream isn't an issue. (Chinese medicine has an explanation for that, but I don't know the details.)

But, among non-frozen things, IMO if it's not good enough to take some of it home, it's not good enough to order in the first place. So it's only usually an issue when we're traveling and don't have a refrigerator or microwave in the room.

DH and I were eating "tapas" before tapas was fashionable. A salad each and three appetizers to share is usually plenty (more appetizers if we're not each getting a salad). Besides, even in the best restaurants, the chefs usually give more attention to appetizers than entrees. So we get the best they have to offer. In a chain restaurant, a salad bar plus an appetizer is plenty.

I did do exactly the same as you, Mimi, recently when I got some movie popcorn. I tend to snack mindlessly at the movies. I ordered a "small" popcorn, looking at the display bags, but it turned out that the size I wanted was "child." The "small" one I'd actually ordered and paid for was ginormous. So I made the worker pour half of it out.