Good at WHAT, exactly?
Your job? Not running people over while driving? Resisting the urge to purchase a Bazooka with which to take out that annoying neighbour?
Or do you mean that you have followed all the food rules and not eaten anything you shouldn't have?
Remember when we were kids and our parents would discuss our behaviour that day? "She was SO good!" And we would feel proud. "You won't believe how bad/naughty she was." And we would feel humiliated.
Food is food.
Really, that's all it is. We decide to charge food up with emotions. Cupcakes - bad, tempting, seductive, naughty. Carrots - healthy, a good choice, diet food. Cupcakes are just cupcakes and carrots are just carrots.
When we tell ourselves that we are "good" or "bad" in relation to food, we are giving it power over us and our emotions as well as how we see ourselves. If we stick to our food rules, we are GOOD. If we don't, we are BAD.
And telling ourselves that we are good or bad - and we more often tell ourselves we're bad - has an impact. Words have power. They come to rest in our sub-conscious. The subconscious creates how we behave in the world.
Eat. Enjoy whatever you eat. The food is neither good nor bad. How you perceive yourself in relation to it, is. And that perception is something YOU have power over.