Our Lord had no need to undertake the bearing of the cross except to attest and prove his obedience to the Father. But as for us, there are many reasons why we must pass our lives under a continual cross… We readily esteem our virtue above its due measure. And we do not doubt, whatever happens, that against all difficulties it will remain unbroken and unconquered. Hence we are lifted up to stupid and empty confidence in the flesh; and relying on it, we are then insolently proud against God himself, as if our own powers were sufficient without his grace.
He can best restrain this arrogance when he proves to us by experience not only that great incapacity but also the frailty under which we labor. Therefore, he afflicts us either with disgrace or poverty, or bereavement, or disease, or other calamities. Utterly unequal to bearing these, in so far as they touch us, we soon succumb to them. Thus humbled, we learn to call upon His power, which alone makes us stand fast under the weight of afflictions.
-John Calvin, Institutes of the Christian Religion-
The Fight of Faith 