REALISTIC GRAVITY - Please help

I have manged to pin down a 2D sidescroller using the x axis only and, a forcecompenent gravity applied with clamp collision on so that it sticks to the ground... Only problem is when the player faces an 80 degree wall, it decides to slide up the wall, just how do i make it more realistic, so it does not do that and instead, will slide down steep walls, giving a more realistic effect... please help...