When vaulting, try not to separate your legs too much. This is a common mistake because intinctively you try to pass one leg before the other, but you have to take'em both at the same time when vaulting, And for landing on rails train balancing over them first, this way you'll know where to put your feet when landing on them.
If you want to monkey or kong over them, try to make your knees touch your chest while pulling yourself forwards, and try looking for tutorials in all these valts and learn the right way to do it, so neither your feet or your knees will catch with the rail.
And try to remember that the pain is temporary, and that these simple vaults won't get you more than some bruises and scratches if you fall, you heal fast and the goot thing is that you'll have realised that the fear made you fall, and won't fear again.
Hope these tips work for you.
Peace.
