If you've taken on a role that's too much for you, you've done two things wrong. You've failed at that role. And you've abandoned a role you could have handled well.
If you have assumed any character beyond your strength, you have both demeaned yourself ill in that and quitted one which you might have supported.
A statement like "either it is day or it is night" works well when you're making an either/or argument, but it's useless when you need both things to be true at once. Similarly, at a dinner party, grabbing the biggest portion might satisfy your hunger, but it completely goes against the spirit of sharing a meal together. So when you eat with others, don't just think about what the food does for your body. Think about showing proper respect to whoever invited you.
As the proposition, “either it is day or it is night,” has much force in a disjunctive argument, but none at all in a conjunctive one, so, at a feast, to choose the largest share is very suitable to the bodily appetite, but utterly inconsistent with the social spirit of the entertainment. Remember, then, when you eat with another, not only the value to the body of those things which are set before you, but also the value of proper courtesy toward your host.