Stress and challenges bring out the character in people, not from a standpoint of understanding mental illness, but how we respond personally. Joni Eareckson Tada has some words of wisdom that hits home for us here and hopefully will be edifying for you.
The verses that Joni cites is Proverbs 10:19-21, here is the New International Version:
Sin is not ended by multiplying words,Proverbs 10:19-21 (NIV)
but the prudent hold their tongues.
The tongue of the righteous is choice silver,
but the heart of the wicked is of little value.
The lips of the righteous nourish many,
but fools die for lack of sense.