Old cure, fold a towel in half lengthways & in half again. Place it lengthways dow the the approach at the foul line approximately 2-3 boards left of the board your standing on (right if your a lefty).
You wont fall over cause you wont step on the towel, however, mentally your brain will tell u, theres a towel there if i stand on it I'll fall over. This worked for me (albeit a long time ago) and it does take some practice.
hope it helps