I'm betting that eating those 320 calories worth of cookies won't do a darn thing on the scale on Friday, especially if you pick yourself up and get back on plan right now
. You slipped, you didn't use your calorie budget wisely today (although you said you will still be within budget), but that's ok. Sometimes we have days like that. The key is not to let 320 calories become 640 and then 1280 and then... you get the idea. Just keep on keeping on and look at it as a minor slip (which it was.)
It's a little like buying something you didn't budget for. You stay within your budget for the rest of the week, adjusting as you need to for the slip. You don't go out and spend the rest of the money in your bank account on frivolous crap because you made a mistake with one purchase.
You're ok, don't sweat it!!
"It is not the critic who counts; not the man who points out how the strong man stumbles, or where the doer of deeds could have done them better. The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood; who strives valiantly..."