A Game of Thrones
How we cite our quotes:
"You know what I must do."
"Must?" She put her hand on his good leg, just above the knee. "A true man does what he will, not what he must." (46 Eddard 12.69-70)
When Cersei tries to seduce Ned (after he's confronted her with her treason), she lays down this thought on him: a real man doesn't let his principles hold him back. Certainly, since Ned has principles, he is somewhat limited – he can't run around killing people, for instance. That's good news, right? But do you think that there's something weak, or even stubborn, about always sticking to your principles?
The king heard him. "You stiff-necked fool," he muttered, "too proud to listen. Can you eat pride, Stark? Will honor shield your children?" (59 Eddard 15.11)
There's one major hitch in Ned's reliance on his principles: they may work against him in a major way. As a father, Ned has a duty to do certain things (like protect his children). So what happens when Ned's duty as a parent conflicts with his principles as a person?
"Then Lord Eddard is a man in ten thousand. Most of us are not so strong. What is honor compared to a woman's love? What is duty against the feel of a newborn son in your arms... or the memory of a brother's smile? Wind and words. Wind and words. We are only human, and the gods have fashioned us for love. That is our great glory, and our great tragedy." (61 Jon 8.96)
Aemon lays this out for Jon: we all have some principles (well, most of us… well, at least Ned does), but there are many times when our principles might not be strong enough to change our minds or our behavior. And considering that Eddard confesses to a crime he didn't really commit, we might agree with Aemon here.