Screwed up

I know exactly how you feel. We all do it because we're human. All the negative stuff you're throwing at yourself now will not help you to get where you want to be. Talk to yourself like your best friend would, like yourself as your best friend does.
You've had a good five days, that's excellent. One bad meal won't take away from the habits you're learning that will keep off the weight in the long term. It's not all black and white, try to cultivate the grey.
Today is a new day, treat it like the first one again and in a few days it'll be forgotten and you'll be a little lighter.

'Walky slowly catchy monkey' as my old history teacher used to say.

It happens and there will be other times you overindulge, dust yourself off and continue logging. This is new to you, any change takes time. Beating yourself up or depriving yourself will just lead to extra overindulgence and the cycle will continue. Make logging a habit and allow yourself to enjoy things. As you go you will decide what events or reasons are worth the extra and you will budget for them, work for them (earn calories) or just not give a f*** and write the weekly loss off as not going to happen.

Enjoy life, it's much too short.