Just a recollection from a book on child-rearing -- one of the two or three books I've read in Finnish, by some Finnish guy you've never heard of -- on how growing up from toddler to even reasonably reasonable individual (i.e, the average eight-, ten- or twelve-year-old) was precisely learning to deal with disappointment. Related to deferred satisfaction and all that, if that sounds more familiar.

So if growing up is about dealing with disappointment, then leadership might perhaps actually be about the "correct" amount of such to demand your followers to take...?

Doesn't seem to be worth dismissing totally out of hand, IMO.