I always swore that when I said "No" I would stick to it. But what I actually do quite often sometimes is say "No... no ... noooooo .. NO ... oh all RIGHT then but ONLY one sweet / just a quick go on the Wii / whatever"
I also swore that I would never wipe my baby/toddler's face on their own tshirt, but when you're faced with yards of snot and dribble in the middle of the shopping centre and you've run out of muslins and tissues and if you wait until you get to the shop that's a few yards away the snot/dribble will hit the floor, what else are you supposed to use?
Ditto if you're just too lazy to get up to find the muslins/tissues 
Let them eat dinner in front of the TV (N.B. I don't allow this every day!)
Make them change out of their school uniform when they get home (who cares? M&S school shirts are cheaper than ordinary clothes, so the DCs might as well keep them on and I buy enough to ensure that there's one for every day of the week). Lazy, moi?
Let them eat something that's been dropped on the floor. I make a snap judgment re. the cleanliness of the floor. I know loads of mothers who have a blanket rule that food on floor = food straight in the bin. Why can't I be like that?
Just re-read this and I am shocked by how slovenly I sound! My DCs are clean and well-nourised, I promise, and my house is actually quite tidy and reasonably clean >