Is it normal to feel like im going to fall

On activity weekends there is more than likely to be a high ropes course.
Give me a harnis and i will climb to the top no problem its getting down thats thats the problem.
On my way up i say to myself i will do this i will stand on top of that pole and reach for the trapeese or wat ever it is but when i get to the top i freeze and have a sort of panic attack and start to cry.
I feel as it im going to fall even though i no i am securely attached and i just hold on for dear life.
Is this normal??