Oooooh when I used to do WW -I got into that habit and it got so out of hand I ended up doing this:-
*weighing in on Thursday and then rewarding a loss or commiserating a gain by eating what I wanted Thursday -which led to eating to much Friday/saturday - well by then we were at the weekend so ooohh a bit extra won't hurt.... I finally "tried" to get back on track Monday -and pretty much starved Tuesday/Wednesday to claw back in time for Thursday weigh in and then off I would start the cycle again
When I started SW I promised myself I wasn't going to get into this habit again -and so I refuse to "treat" myself with food (although I make sure I have lots of lovely meals planned each week-so I don't need anything else)-I hop on the scales Sunday morning and then straight back down stairs for brekkie and to start another week,
Im like purplesky -I sit down on a Saturday and plan my meals for the week so come sunday morning Im all set to go..
I do treat myself but with a nice candle, smellies, face pack etc...
I know it sounds bonkers but Im one of those that find it much easier to stay on plan than to go off slightly and then have to try and get back on again