Halloween:
I buy candy I don't like for the kids. I don't like coconut, so I buy Almond Joy and/or Mounds to hand out. I'm not tempted to sample them and when I bring the leftovers into the office, I'm not tempted to eat them. Now if it were Reeses or any other form of chocolate, I'd be inhaling them, so I make it easier for myself by not bringing the stuff into the house. I may have one or 2 around the office when someone else brings it in as leftover candy, but then I feel I have to keep consumption to a minimum so as not to be known as the co-worker who snarfed the Reeses

Thanksgiving:
I'm usually a guest at my great-aunt's house. I bring some munchies I can eat(veggies & nonfat yogurt dip) while we're waiting for dinner to cook. And a side dish of green beans. I eat whatever I want on the one day, I just keep it to the one day. My great aunt always offers people leftovers. I skip the mashed potatoes & stuffing (much as I enjoy eating them on Thanksgiving Day itself) & stick to turkey & veggies for the leftovers. This way, the one day doesn't turn into the Lost Long Weekend.
December:
I used to use all of the shopping and errands as an excuse to skip exercise. I try to shop online whenever I can to save time so I can do my workouts. I still bake Christmas cookies, but far less than I used to. I supplement them with Clemintines for variety for the people I give them to & so that I don't have excess cookies around the house. I do leave excess Clemintines. I moderated my meals. If I know we're going out for lunch at work to celebrate or the office party is in the evening, I'll have a salad for dinner (if it's a heavy lunch) or lunch (if it's an evening party).



Halloween: Last year, and probably this year, we didn't have any trick-or-treaters so I gave the candy to my husband to take to work. That wasn't a big deal because I'm not really a sweets person. In years past, I've gotten cheap little toys from online party favor distributors and kids love that.
Thanksgiving: Last year, it was a success. Instead of mashed potatoes, we had roasted red potatoes and green beans instead of green bean casserole. We had mashed sweet potatoes instead of sweet potato casserole. We did have stuffing and this broccoli/cauliflower/cheese casserole that I make. We had pumpkin muffins instead of pumpkin pie. This year, I am going to cut the portions down some (at least on the bad stuff) and try to lighten up that broc/caul/cheese casserole. Last year, I measured out everything I ate and I think I will do that again this year. I am lucky in that we have Thanksgiving at our house.
Christmas: Christmas eve, we go to my mother-in-law's house and she usually makes some sort of dinner but it isn't the traditional turkey dinner, it's more like a regular semi-healthy meal. For Christmas day, it varies what we do but this year, I think I am going to suggest going out to eat. That way I can eat what I want but not have leftovers or the dirty dishes!
New Year's Eve/Day: Instead of the traditional pork and sauerkraut, we make this awesome smoked sausage and sauerkraut soup. We use turkey sausage and it's pretty healthy.