This is indeed true. I've seen God restore to me parts of me that I'd thought I'd lost. I've seen Him give me a new heart, a new mind. I've seen Him put new sinews into me, spiritually speaking, that weren't there before.
i am thankful for all those difficult people in my life. they have shown me exactly who i do not want to be. Hypocrites and the like who act one way at school and behave totally different in their homes. People who believe in one thing but act another.