I find if i start having the naughty but nice stuff ( chocolates, pastries etc) then it makes it so so much worse to get back on track, its like it kicks in the cravings all over again, which when i am on plan for a good while i dont get the cravings. bit like a alcoholic cant just have one drink, it will lead to the cravings big time.
I find it just easier to stick to plan, i sometimes have and extra Hi fi bar, or anther bowl of cereal, but still of on plan foods, just more than i *should* have had in a day.
I went to Burghley horse trials for 3 days, put on 4lbs.... but took me almost all week to get back on plan again, as i'd had sugary foods and chocolate etc, and i just craved it all week.
Had to go through the cold turkey all over again.