According to the dictionary, indulge means "To yield to, satisfy, or gratify (desires, feelings, etc.)." It doesn't say to yield to, satisfy, gratify until you have to unbutton your jeans because you've gorged in gluttonous rapture. There is a big calorie difference between enjoying one sliver of pumpkin pie versus inhaling half the pie. Sipping half a cup of Egg Nog is not going to break your calorie credit like swigging the whole carton.
The reason many of us will gain a bulge over the holidays is not because we let ourselves partake in the goodies and scrumptious home cooked meals. We gain weight because we devour holiday food like we're going into hibernation compiled with the fact that we are not balancing the extra food consumption with more activity, exercise, or movement. Because it is colder outside and the days get darker sooner, we are more inclined to sit in front of the computer or TV than go for a Winterland stroll with our sweetie or ice skate in the park with friends.
This holiday indulge in your favorite foods and drinks because life is too short not to luxuriate in delicious food. Just be conscious of portion control. Nibble versus gobble. And don't forget another delectable indulgence, kissing under that mistletoe. All that smooching is a merry way to burn calories.