Utilitarianism -- chủ nghĩa Thực dụng, is an ethical theory which states that the best action is the one that maximizes utility. "Utility" is defined in various ways, usually in terms of the well-being of sentient entities.
As long as I keep fighting for us, it means that I will do everything I can to keep us alive. When you don't hear from me anymore it means that I'm done being the only only fighting for us. And I've forgotten your bloody existence.