Touch that wall. This you do for 25 hours. Then you do it to another student for 25 hours. And after that there is a dozen or two other Objective Processes of the same sort. Of course this in the end creates tough students and Soloist who can get through anything no matter how hard it may seem.
Most students decide they are tough enough after one time through the above.
Hopefully you don't need any of that. Just get the idea. Actually erasure of unwanted things in the Mind has very little to do with toughness. It has to do with peace of mind, willingness to peacefully feel anything in Solo without running away. Willingness for Truth.