I find that taking a deep breath myself, keeping a calm demeanor and getting my body between what is frightening him works, when done consistently. Just keep walking, calmly. I would give a treat and praise him immediately AFTER he has passed his apprehensive situation. Giving him praise and a treat prior or during the uncomfortable period, only reinforces his actions. He's getting the message that as long as I stay nervous, I'll get a reward. I think the previous comments get the idea.