How do you handle the day after giving in to late-night snack temptations?

I've been managing my diet by limiting calories...
Yesterday, I had only eaten my allotted amount,
but after stepping out for a bit late at night,
I couldn't resist the temptation on my way back and ended up buying a hamburger from Burger King.
And it was a big-sized burger, too.
I've been feeling guilty all morning.
For those of you who usually manage your calories, what do you do in this situation?
Do you just stick to a normal diet today, thinking "yesterday is yesterday and today is today"?
Or do you think, "I ate so much yesterday, so I should eat less today"?
I'm currently debating whether or not to eat lunch....