Imperfect but forgiven
I believe that but then I hear stories from Persecuted Christians who had nervous breakdowns during extreme torture. I remember our flesh is weak. I do believe even then, we can still hold on to our Faith, only with the help of the Holy Spirit, even if we are falling apart physically and mentally.
Our minds and bodies have breaking points, that's for sure. However a Believer might suffer they won't be alone. The Comforter is there with us.