Staja, I find it hard to regroup when my plans are disrupted, too! Logically, you can say, "Just replace it with something with the same calories," but realistically, being thrown off-kilter can be very disconcerting. Also, I've found that if I'm not eating what I wanted (like that burger -- yum!), nothing else satisfies, so I keep eating, and eating...
But now that's behind you! Pick yourself up, dust yourself off, and make this a better day!
Back in the saddle. Again.