Only concrete on the bit of wall your at don't look down don't even look all the way up just concentrate where the nearest hole is. Also before you go up calculate your route and split it into sections and beat each section instead of trying to conquer the entire wall. Good luck
You need to trust the system - The system never fails!
Like somebody said above, concentrate on whats infront of you, and the next 2 or 3 moves ahead, forget about what is below you.
Alternatively, have somebody drop you a few feet over and over again. Eventually, build up the distance of the fall and you will, get over the height and learn there is nothing to worry about! It's a shock tactic which is tried and tested!:nunu: