Recent events in my family of origin have highlighted how easily we revert to/hold onto a flawed view of God's grace and human fragility.
Unfortunately, it seems that God allows a whole lot more ambiguous and painful things to enter our lives than we were led to believe in our younger days. There was definitely a teaching that if we followed Christ perfectly we could be spared most of the nastiness of life. Turns out that bad things happen to Christ followers, too. Faith, prayer, legalism, etc. can't cure mental illness.
Funny... Legalistic Christians can accept cancer, disease, tragedy, etc. as just the experience of every life, but there's a bias that believes that mental illness hinges on a right relationship with God. Now, that's a slippery slope that we watched our mom slide down. Repeatedly.
Mental illness was the background of our family relationships. As was faith in an omnipotent God, and his call on us as Christ-followers to walk a righteous path.
The fact that my siblings have built healthy, loving families who continue to walk with the Lord is precisely attributable to prayerful grandparents, parents, and aunts and uncles. And, to God's grace and unconditional love.