I used to be terrible with hifi bars, so I just don't buy them now. I'd have one in class (after not eating since lunch, in preparation for WI!), then another when I got home while I was waiting for my dinner to be ready, then another one after dinner. I just can't trust myself with them!!
I just don't buy things like that now, then if I want a treat I have to actually think about it, and decide whether it's worth the 2 mile walk to the shop and back. If i do venture up to the shop, I generally feel good about walking and by the time i'm there I only buy a low-syn treat. Where as if I stayed at home with snacks around, I probably would've ended up on a kitchen safari!!