I have been climbing the carob tree above a carpark, it's full of "CHOCOLATE" and although I am high up, I only move one (of 4) things at a time; either a hand or a foot. 3 points of contact at all times. What you said about fear of falling reminds me of this parkour classic...

CHOOSE NOT TO FALL.
RE: Zip-lining & tree climbing: a tale of caution?