The problem with this viewpoint is that in a class society of oppressors and oppressed, oppression becomes virtuous. "Without us no one would work." In our society, the people who promote this philosophy are not usually the sufferers, and when the sufferers do promote it it is an internalization of the ideology of the oppressors.

In fact, this is a very limited view, that hides the actual process. What is really happening, is that you have an individual subject. That subject has to be understood as a thinking, feeling, experiencing being. They have some experience of the objective world, they contemplate that experience, that contemplation initiates changes in the subject, and then the individual acts based on the understanding of the experience. That activity changes something in objective reality; which the subject experiences, contemplates, understands, and acts upon.

Our society, including this meme, neglects to define this thinking/sensing/experiencing subject, and what is objectively recognized is socially determined, mostly by whoever is in charge, who uses direct and indirect domination to enforce and influence the way that the oppressed, the sufferers, define and understand their direct experience of suffering.

While there is some truth buried in the meme, for example if I experience suffering I may contemplate it and change something about my practical activity in order to end the suffering; suffering does not equal positive development in the subject. Most often, it results in a kind of trauma if the individual is not able to change their circumstances. Something as simple as tooth-pain can completely derail ones ability to think straight and make rational decisions. Its suffering, yes, but if you can't afford or access appropriate dental care, that doesn't mean you like become a better person. "Whatever doesn't kill you makes you stronger" can be a kind of cope, or survivors bias. Sometimes what doesn't kill you permanently maims you. If you adapt, then yeah maybe. But even in adaptation, disabled people face all kinds of obstacles to access, safety, dignity and prosperity. If the meme was universally true, then disabled people would be undeniably titanic superhumans; and frankly, some of them are. But you wouldn't know it, because actually society shoves these people down, leaves them at a disadvantage that always has to be fought against.

Even if someone is theoretically "stronger" if they encounter more social challenges then the weaker and more privileged will still get ahead, which is exactly how things work. The most successful people in society cause most of the suffering, and actually suffer the least. So the meme has some truth in it but only in the most narrow and idealistic way. In reality, most suffering leads to internalization of the causes rather than a fighting spirit to overcome it, which is exactly why the oppressors oppress. If suffering really made people stronger, then it wouldn't suit our rulers to make the masses suffer.

Don't fall for the cult of the individual. Strength comes from unity.