Question

How can fear be beneficial?

Answer 1

Lets say you were scared of getting in a car with a stranger, that fear would be beneficial because you would avoid future problems. Basically, sometimes fear can keep you safe

Answer 2

A fear of something, say you are afraid to go through an alley, is beneficial, because you can elude unknown harms along the way. Fear, would usually let you rethink what you are about to do and search for a better route to the same destination

hope this helps