I previously concluded that the quote is misleading, as some suffering will weaken you. But I am also convinced that suffering is an important part of learning and development. In the physical domain, we improve our physical strength and stamina via repeated exposure to painful training, and we improve our skill through practise that can be both physically and mentally draining. Similarly, our mental faculties improve through practise, which is often taxing.
That suffering is essential, and that too much is detrimental, suggests there is an optimum. And hence a question of fundamental importance: what is the optimal level of suffering? I strongly suspect that the optimum will vary significantly from person to person, and throughout each person's lifetime. So we should ask ourselves the question: are we at the optimum level of suffering for growth without detriment?
There are some complications: answering that question is difficult - as both measuring the level of suffering, and measuring the potential for detriment, are inexact; and because in an unforgiving society we cannot push ourselves to the limits as we cannot afford to fall over. We have to keep a safety margin between ourselves and the optimum. Alone we cannot push ourselves to our true limit, because there is no-one there to catch us when we fall over.
Which brings us back to the importance of a teacher, one that both imparts information, and pushes the student to deliver. When I try to imagine an environment of a teacher that really pushes students, I am reminded of some of the stereotyped images of military training, where the drill instructor pushes recruits to the limits, whilst trying not to push them to far (a la "Pyle" in Full Metal Jacket). I am also reminded of the scene from V for Vendetta where V imprisons Evey until she is free of fear.