It depends on what kind of fear. Sometimes fear will stop us from doing stupid things. Someone who is afraid to die will do everything to keep themselves alive, someone who is afraid of fire will make sure they don't accidental leave the gas running and so on. Some fears are not needed or irrational, like the fear for spiders, clowns, your own shadow, etcetera. Those things are not really good. I had a friend with a fear for birds and he was driving his car and suddenly a bird flew over, I swear he suddenly had his head beneath the steering wheel to 'hide'. Those fears are not good for they can cause you and the ones around you danger
So it depends on what kind of fear and in what measures it is felt. Some feelings of fear are exaggerated, making them unreal and not good.