I do agree that some relatively small amount of suffering is a good learning experience, especially for kids. Mostly, they learn that what they _think_ is huge suffering (delayed gratification, having to share, being polite to people) is in fact not suffering at all. Long-term, I think this leads to greater happiness in life, so the suffering is justified.

But as the sibling comment noted, this can be taken too far quite quickly. Based on what you wrote, one could say that literally torturing people (crushing trauma) is good for them. Hopefully you don't believe that. I think it's pretty clear that suffering past a certain point ceases to be instructive.