Fear - a distressing emotion aroused by impending danger, evil, pain, etc., whether the threat is real or imagined; the feeling or condition of being afraid.
Many years ago I was attending a parade; it was a city parade and I was in one of the city shelter wagons. We brought our dogs and waved to the crowds. I thought it would be fun; but not so much. Anyhow; there was several others in the wagon and one person had a dachshund that was quite fearful. Also in the wagon was the resident shelter trainer; was not me. I was a newcomer and to many of the long timers; I was a person with weird positive training ideas. So this very harsh conventional type trainer told the woman with the doxie; to yank him. When she gave him a gentle yank on the choke collar he abruptly grabbed the collar and gave an almighty yank. It was horrible; not only was the dog in a state of fear because of all the comings and goings, noise and people but the little dog had now received a severe reprimand; for what?
Fear belongs to the person who is experiencing it; no one else. Whether or not we feel like there is a need or reason to be fearful means nothing. What you need to do is to address the fear response no matter what the fear trigger is. How do you do that? Keeping chill are rewarding calm or calmer behavior. The worst thing that you can offer your dog in response to a fearful display is soothing touch and words. When you try to console a fearful dog; you are telling the dog that there is in fact an issue to be fearful of.
Your dog will be watching you; and however you respond to the trigger, your dog will take in. Often when my guys are startled by a surprise noise or object; I too am startled but I quickly pull it together to appear calm, cool and collected. It is amazing how quickly it can diffuse the situation. Just yesterday I was skyping in bed; my bedroom door started to blow shut and I did not have the time to get out of bed and run to stop it. Luke is petrified of slamming doors; so as it slammed and Luke bolted up I did nothing. I sat and chatted like nothing had happened. He looked at me; the door, me, the door and then lay back down. Had I even acknowledged what had happened; I would have drawn the fear response into a much longer span.
Often a fearful response will be triggered and catch you totally off guard. About a year ago I was taking the dogs to a new beach; we had to walk through a tunnel like thing to get there and Tilley had a very strong fear response to the surrounding environment. I had not expected it and was not ready to deal with it. She was frozen in place; not wanting to yank on her I simply hoisted her up and carried her through. I placed her on the ground as we exited and continued like it was just another day at the park. Now I realize that she is quite afraid of bridges or anything like that; we've been working on it. She is not over it but will walk over a bridge now; we just do it. There are no treats involved as she is too afraid to eat; I just give her a very good lead to follow, nonchalant and away we go.
Don't try to explain away a fear; it simply doesn't work with our dogs. Not only does it not work; but it makes matters worse. Show your dog through your actions that there is nothing to fear. Often you need to do a really great acting job; you may have been startled or be afraid yourself, don't show it. Unflappable; that is the image you are going for, can you portray rock solid or cool as a cucumber?