Need Encouragement

Started IF and Ketoish diet on 5/31. Today I’m down 9 lbs. Yes it’s water weight, but still 9lbs less.
Today I ran into the grocery store for some cheese and darn it, right in my face were these personal sized key lime pies!! Excuses I made in my head were, well, I’ll just have a little piece and give the rest to my son......another was, I read somewhere that you get kicked out of ketosis if you consume >50g of carbs, I think....and a little piece will be way less than that...
Either way, the fatty in me bought it! I came home, prepared my meal, ate then cut about 1/4 slice and OMG! It tasted soooo good!
But now I feel like a failure. How bad do you think the consequences of my weakness will be? Be honest......but speak to me nice!! Lol