Wel, I was just like you 2 weeks ago, doin awesome and losing weight. I slipped up, and I felt awful..well then I was totally off plan for a whole week, and gained 3 pounds, now Im back on track..with 3 extra pounds to lose..SO...moral of the story: DONT let it get you down, and FORGET that you ate those cookies..it will only continue to bug you. Eat a sensible, healthy dinner, and if at all possible, squeeze in a workout dvd at home, go for a quick powerwalk, or if time is really an issue, do 50-100 jumping jacks..it gets your HR up and its so better than nothing! It might make you feel more productive, and encourage you to stay on plan for the rest of the week. Tomorrow is a NEW day, a clean slate, so please dont let the slip up cause you to fall away for your plan. SLIPS are fixable, Falls, are much worse.
Good luck hun, and do those jumping jacks, im telling you it works!