I don't get it

I'm exactly the same way. In order to snap out of it I need to "ground" myself a bit - eliminate decision making and choices. Plan out at least one week, preferably two - every meal, every bit of free time. Plan, prepare and pack every breakfast lunch and dinner. Figure out what you're going to do with each bit of non working time so you aren't going to snack, whether it's go to the gym, go for a hike or focus on a cleaning project in a different room each night that week. If you usually come home and grab a snack and some couch time - don't - immediately grab a water and start on your planned activity. I'll also avoid socializing as much as possible - just too tempting. I find getting super rigid with myself for a bit resets the good habits that started to slip. Just came back from two weeks vacation and while I didn't get too crazy I'm in reset mode myself right now.