worrying and obsessiveness comes from not knowing. you're always wondering " do I look fatter than yesterday?" , "will this food make me fat?", "will this fast food mess up everything I've done thus far?" etc etc. set standards for yourself such as work out for 25 minutes a day and eat within the first hour of waking up and don't eat for 2 hours before bed. as long as you stick to your standards of what you must expect of yourself don't worry about much else. I may also set standards such as fast food only once a month and only a certain amount of calories or sugar per day e.g. 1350 calories and 25-30g of sugar.
Well first of all you can start by not eating late at night, yeah everything tastes great at night I don't know why. Next you can eat whatever you want but also work out? Working out definitely helps! Ahd last don't eat junk food ALL the time. Good luck!