Use to read a book. There is a middle class family with quite lot of children.... with a mother whose favorite food is fish head so that in every meal whenever there is fish, her husband and children will leave the head a side for their mother to show their love.This continuing for years till one day when the mother get old and sick... her children sit around her and try to feed her with rice and fish head, try to serve her as best as they could for their mother who has been take a good care of the family. The eldest son said "mom, here i bring you your favorite fish head, eat some."
Suddenly this old lady burst into tears and cries like a baby. She said "i'm sorry, i'm so sorry. i am so regret." Her family try to convience her that there is nothing to regret nor sorry for. She did a very great job for the family. Then she answer"No... i'm not feel sorry for you, I feel sorry for myself. I spend my whole life to serve all of you, to put all your needs upon mine, i don't like fish head at all, i hate them. There are so many thron that will sting my tongue. I told you i like it so that you people can eat more without feel sorry for me."
And here is my conclusion; as a guess, your "respect" controls your desire to eat too much in front of the host. As a host, your "manner" controls your desire from eat too much in front of your guest. As family member, your "love" controls your desire to eat too much. You want to leave it for other family members.
So when can you eat as much as you want??? of course when you are like me now... alone in the middle of no where... you don't need not life for others, need not worry about what will people say. This is privacy, this is all about your own life isn't it? hekhekhek