Read about his life on wiki and was quite moved by what he said
when he got cancer:
http://en.wikipedia.org/wiki/John_Piper_(theologian)
On January 11, 2006, Piper announced that the month
beforehand, he had been diagnosed with prostate cancer. According
to a letter sent to his church,[1] he and his doctors believe that
the cancer is fully treatable. Piper's reaction to his diagnosis
was: "This news has, of course, been good for me. The most
dangerous thing in the world is the sin of self-reliance and the
stupor of worldliness. The news of cancer has a wonderfully
blasting effect on both. I thank God for that. The times with
Christ in these days have been unusually sweet."
Only by acknowledging God as sovereign, acknowledging that we need
to fully depend on God will we grow stronger and faithful. You do
not need miracles or healing sessions to show God is in control and
still affecting people's lives. God is all-sovereign and no matter
what happens, he is in control.