Machines & systems do indeed break so designers & manufacturers invest (large amounts) of time & money to make them better, more reliable & therefore less likely to fail.
Through better design they become more reliable.
Pilots are subject high stress loads requiring high degrees skill & competence, depending on the scenario. As one of the human elements of the "system" of course it too can fail & will fail under certain stresses. Just like a spar that has a defined loading limit. How well designed & manufactured will define that breaking point.
The same can be said for airline pilot training & standards.