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.
John American Standard Bible (NASB) 16 You did not choose Me but I chose you, and appointed you that you would go and bear fruit, and that your fruit would remain, so that whatever you ask of the Father in My name He may give to you.
"Lord, if it's not your will, let it slip through my grasp and give me the peace not to worry about it anymore." - however, if something is going to slip through your grasp it may require actively opening your hands