How can I stop eating so much at family holiday dinners?

Drink H2O.Small port. Drink 12 oz of ice water before eating, and simply serve smaller portions.
Be selective. Holidays are for sharing and enjoying families and friends. The food may not always be the healthiest, so eat a bit of protein and take a few portable munchies, celery, or carrots, cucumber slices, with you. Drink a few glasses of water before hand and sample the foods rather than pile them on. You will enjoy the remainder of the year in a healthier state.