Cedric is upset by this point---partially because he knows Howard is right, and partially because he's afraid of what will happen when the whole situation is beyond his ability to help. On whether they win or lose, he has no influence. Powerlessness scares him more than just about anything else.

"I'm not going on the front lines, or outside, I know I don't belong there," he huffs, "but I will find a way to support everyone."

Pent-up anger from years of mockery at school is bubbling over. He remembers comforting distraught first years in the school common room, hearing taunt after taunt about the house of duffers. Hufflepuffs are useless, they've never contributed anything to our world, the other students would say.

Bravery's not just a Gryffindor thing.