Have you tried testing your harness to prove to yourself that it will hold you? I saw this on a tree stand safety video,have a friend help you with this test. hook yourself to a tree just high enough so you can stand on the ground, Then lift your feet off the ground and all your weight is on the harness, this will give you the opportunity to see how you should react if something were to happen.
Heights don't really bother me but this sounded like a good idea. Good luck!