I've never had anything that I quit fearing because I did it. I don't ever remember fearing snakes. For as long as I can remember, my Dad would catch snakes and turtles and let me handle them. He'd be driving home from work, see a turtle in the road, and put it in the car for me to see. (It's probably illegal to do that now.) The result is that I've always found reptiles interesting and not frightening.
I've feared heights for all of my life. In college, I took up caving and had to do some rappelling and climbing. I never quit being afraid and was never very good at vertical caving skills, but I learned to put those fears aside enough to be a competent caver.
Where the other side happened is with claustrophobia. For most of my life, I had no problem with claustrophobia. I had no trouble flying or being in other slightly closed situations. In 2000 and 2001, I had to fly from Houston to Seattle on business on five occasions. I guess I shouldn't name the airline, but their flights were horrible and uncomfortable. I also had one bad flight from Atlanta to Houston on another airline. Nothing dramatic happened on any of these flights. They were just uncomfortable as flights. To make matters much worse, I reached an age where my joints swell when I fly. After about an hour or so, my feet were too big for my shoes. I'd untie and loosen my shoes, but I could barely walk when I left the plane.
The result of these bad flights is that I developed claustrophobia. I can't fly anymore. Maybe in an emergency I'd have a few flights left, but I'm not certain that I could fly at all. I also have problems in crowded restaurants, particularly if I'm sitting "inside" in a booth, and in meeting rooms. Occasionally, I'll have a reaction if I see a shot on TV of a crowded room.
To make things stranger, one symptom of claustrophobia is supposed to be a fear of wearing respirators. However, I'm on the fire crew at work, and I've never had any problem wearing a respirator or participating in training that requires me to go inside buildings in full bunker gear.
Bill