I had the same problem with persicions and still do to an extent. Start out with shorter ones, and at ground level to get more and more confident, like trying to persicion the parking lines in the lots and get his technique down. If something looks bigger than I'm used to I always like to try it out at ground level first. Then just work your way up. As for the thought of getting hurt, that's just where confidence comes in and knowing what you can do. And basically just working to over come that mental block.
As for Vaults, I'd say go with what Nom said. Lol