Remember the term "situational ethics?"  Essentially it means sacrificing your integrity for momentary expedience.  I realized that nearly ALL people in Western Society engage in "Situational Eating (c)" .  They may try and try to eat healthily, to lose weight, only to throw it all out the window because, for example;
a.  The host worked so hard on this dessert, so I really should have some.
b.  The kids left this, and I don't want it to go to waste
c.   It's my birthday, and I deserve a bigger slice of cake
d.   I haven't had home made ice cream in soooooooo long
e.   I have to travel, so there's no way to stay on my usual diet.
f.    I'm stressed
g.   I'm happy
h.   I'm sad
and last, but not least..................................................It's the HOLIDAYS!!!!!!!

Guilty?  Admit it.  I am.  Everyone is to some degree.    
There seems to be a mental "pass" that people give themselves when they want an excuse to over-indulge in food.  Holiday parties are the worst offenders, along with the well-intentioned office employee who wants to "treat" their co-workers by bringing in a dozen doughnuts to the office.   I've seen the office descend upon that box of carbs like jackals on a dead antelope.  Everyone is drowsy and non-productive an hour later when the sugar crash hits, but they'll repeat it the next time without hesitation.   The point is that your eating habits don't have to be tied to external situations.  Eat for nourishment.  Don't eat for fun.  Sorry, but that's what will work.  Our ancestors ate to survive.