moral fiber

Strength or courage derived from moral principles or ethical values. Unfortunately, villains will flourish as long as there are people in the world who lack the moral fiber to stand up to them. We need business leaders with a lot more moral fiber than is being displayed here today.

with every fiber of (one's) being

With the entirety of one's energy, effort, or conviction. I'm going to fight with every fiber of my being to make this company a success! I hate that no good parasite with every fiber of my being. She believes with every fiber of her being that she has what it takes to be a great artist.

moral fiber

Ethical courage. The term dates from the second half of the 1800s. It was applied to World War II pilots who snapped under the strain of combat and refused to fly, and were then accused of lack of moral fiber. Playwright Terrence Rattigan used it in Flare Path (1942): “And on my confidential report they’d put—grounded. Lack of moral fibre” (2:2).