He can best restrain this arrogance when He proves to us by experience not only the great incapacity but also the frailty under which we labour. 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...
In peaceful times [holy persons] preened themselves on their great constancy and patience, only to learn when humbled by adversity that this was all hypocrisy. Believers warned, I say, by such proofs of their diseases, advance toward humility and so, sloughing off perverse confidence in the flesh, betake themselves to God's grace. Now when they have betaken themselves there they experience the presence of a divine power in which they have protection enough and to spare...
And it is of no slight importance for you to be cleansed of your blind love of self, that you may be made more nearly aware of your incapacity; to feel your own incapacity that you may learn to distrust yourself; to distrust yourself that you may transfer your trust to God; to rest with a trustful heart in God that, relying upon His help, you may persevere unconquered to the end; to take your stand in His grace that you may comprehend the truth of His promises; to have unquestioned certainty of His promises that your hope may thereby be strengthened.
Institutes 3.8.2-3 (Battles p703-4)