That's great about your sister!
And being good for 3 days is suppperrrrr... it feels so great doesn't it? At the start of me losing weight I had some 'bleh' days. Not like I eat everything, but my cravings were awful, so I (stupidly) would have a chocolate bar instead of dinner...how insane is that?!? Thankfully those were the old days. You maybe set yourself little goals like "If I'm good for a week, I'll allow myself a vodka", or "If I'm good for two weeks I'll buy myself those shoes in new look" It was doing thinks like that that help me 'train' my body to be good and I can honestly say after months of doing that, my body is now good all on it's own lol! xxx