I ate it. It was good. It was better than good. I have no regrets. Tomorrow will consist of "regular" food and moderate exercise.
Just know that if you occasionally eat something you really want, it is not the end. Just begin again. I wanted this carrot cake for weeks. Now I have had it. I have wanted this weight loss success for a lot longer than a few weeks. The weight loss wins. And so will I. So can you.
Don't give up just because you ate fill in the blank. You can succeed but you have to keep going! No amount of carrot cake or anything else can stand in your way unless YOU let it. Now get moving!