I have two main fears: a fear of man-made heights and a fear of projectiles.
The first is comlpetely nonsensical. I'm perfectly comfortable in a tree or on a cliff. I've stood at the edge of a sandstone cliff with no safety rails and looked down fifty feet to the top of the pine trees below me without worrying. I've also clung to crumbling gniesse over brush infested with Mojave green rattlers (neuro- AND hemotoxin in their venom). Basically, if I'd sneezed I'd have been killed by the fall, the brush impailing me, or the snakes. Didn't even slow me down. But put me on a ladder or high enough to feel the building sway and I start to sweat. I never let it interfere with my work, but I really, really don't like it.
As for projectiles, I think it's fair to be afraid of them after you've dodged bullets and had a few knives thrown at you. Of course, last time someone shot at me I sort of snapped...Apparently I had a k-bar in my hand and was going to cut their throats. I don't remember any of that, or any of the trip to the first aid station (no bullet wounds, just a few cactus spines that needed removed--when you hear the bullets zing by your head you really don't care what's in your way).
I don't know of any fears that stop me in my tracks. I was raised to do my work no matter what. Emotions, including fear, simply are not relevant considerations. If I don't HAVE to be on a ladder I won't be, and I've come up with some creative solutions to get around using them (bleeding has never bothered me), but if a ladder is required I go up the ladder.
Well, in the interest of full disclosure, I AM afraid of a blade in my wife's hands. I've seen what she can do with one, and I know that dagger she keeps next to the bed (I've been stabbed by it twice, by my sister). When I wake her up suddenly and she pulls the dagger, I stop where I am until she puts it away. Doing otherwise is just suicidal when the person holding the blade can call her shots with a knife (I've seen her do it). I don't consider that to be a fear, so much as common sense. I mean, I'm not afraid she'll do it randomly; it's just that in that situation I had to stop or get killed. It IS rather hard to go to sleep after that, however.