I don't know why and maybe it's due to early potty training, but I've always been scared to death of leaking or having any kind of accidents. I've been working on trying to overturn this hang-up for the better part of 12+ years now, but I'm guessing once you develop this mentality, you're pretty much stuck with it. If I wet my diapers and leak in the bed, I will jump up immediately from the dead of sleep, change the diapers, clean myself up and the bed as much as possible. I can't just lay there ether, I've tried and the feeling of "wetness" where I'm lying just bothers me to no end.
I used to be real big into plastic pants, but I quit wearing them because the elastics tend to bite right into my inner thighs. It sucks though, because when I'm concentrating on wetting myself, instead of just going, I find myself trying to get into a certain position whether lying down or shifting my sitting posture. It's basically to try and figure out what's the best way to relax my bladder to keep from straining as much, mixed with where you are trying to maneuver your urine.
I still got one trick up my sleeve, but I've just been too busy all these years to try it. Someone once told me to put down a bed mat for ether in my bed or where I'm sitting and try to relax more without thinking about it. I don't know if this will help me to overcome my fear, but I just may give it a whirl during my next vacation.