ok kitkat, breath deeply!
you haven't done so much damage, if you turn back to your daily routine, in a couple of days everything will be just FINE. you don't need to eat less these days, just eat as usual, 1800 calories if it's that.
just pretend you have been... to a pijama party!
you had to eat!
don't feel guilty, it can happen from time to time, thin people sometimes overeat too in special occasion... just pretend it was a party!
and after all it doesn't have to be bad for sure... sometimes changing the amount of calories... giving a SCHOCK to our body... it's not that bad, it can wake the metabolism up. especially at 23 years old!
so dont' even think about tonight! move on and feel young