Imitation of Christ

Nunc autem Deus sic ordinavit, ut discamus alter alterius onera portare, quia nemo sine defectu, nemo sine onere, nemo sibi sufficiens, nemo sibi satis sapiens, sed oportet invicem portare, invicem consolari, pariter adjuvare, et ammonere. Quantas autem virtutes quisque fecerit, melius patet occasione adversitatis. Occasiones namque hominem fragilem non faciunt, sed qualis sit, ostendunt. 

But now God has ordained, that we may learn to bear one another's burdens, because no one is without defect, no one without a burden, no one sufficient of himself, no one wise enough of himself; but it is proper for us to bear with one another, to comfort one another, to help, instruct, admonish one another. How much strength each man has is best proved by occasions of adversity: for such occasions do not make a man frail, but show what kind of character he has.

Imitation of Christ, I, 16:4