The Time Machine
How we cite our quotes:
Already the Eloi had begun to learn one old lesson anew. They were becoming reacquainted with Fear. (7.2)
While the Eloi are mostly unafraid, there is one thing they're afraid of. How do they respond to this fear? (This seems like the sort of danger that might lead to some evolutionary development.)
Still, however helpless the little people in the presence of their mysterious Fear, I was differently constituted. I came out of this age of ours, this ripe prime of the human race, when Fear does not paralyse and mystery has lost its terrors. I at least would defend myself. (7.3)
Fear can be a productive emotion if it leads to useful actions. Now that the Time Traveller knows what he's afraid of, he seems more confident that he'll take some purposeful action. (Compare this to his other reactions to being afraid.)
I threw my iron bar away, almost sorry not to use it. (10.9)
If we doubted that fear was useful, here's a helpful counterexample: the Time Traveller is no longer afraid of the Morlocks, so he doesn't take the precaution of bringing his weapon with him – and he very nearly loses his fight with them. If he had been afraid, he would have acted more sensibly.