Good evening! And now for your pep talk.
You are OK! You have done great through the holidays and this is your first indulgent evening in a long time. And I bet you don't want to go entirely through life without one here and there.
You will get up tomorrow. You will hit the store. You will get the on plan food you love and you will be right back on task. You won't even bother dwelling on tonight because how is that helpful?
I do totally feel for you. It takes a little bit to just shrug it off, say oh well, and realize in the entire scheme of healthy living - a minor blip.
Drink lots of water. Know you are going to feel bloated and a bit sugar hungover and that it will all pass. Pep-talk that healthy loving mind - tomorrow will feel great.