I am not trying to dishearten you; I want to encourage you to look at humanity from a wider and truer point of view.

Do not be too readily depressed, if you find your faith shaken in a person whom you have hitherto believed to be good.

That person has been led into temptation.
Wait till time shows you that the evil influence is not everlasting, and that the good influence will inconsistently renew your faith out of the very depths of your despair.

Humanity, in general, is neither perfectly good nor perfectly wicked: take it as you find it.

Is this a hard lesson to learn?
Well! it's easy to do what other people do, under similar circumstances.