Something I've realized in recent months is that restaurant portions are insane.

Even if you're not eating a cheeseburger - heck, even if you're eating a salad (assuming it has more than just lettuce) - the sheer amount of food you get in a single entree at most restaurants means that even a reasonable type of meal will end up being two or three times the calories it would be if you made it at home. The alternative of course is to stop halfway (or earlier), but that's really hard to do when it's right in front of you.

The only workaround I know of (beyond just not eating out) is to order it to go, and then immediately put half in the refrigerator.