You will waste your cancer if you do not believe it is designed for you by God.
It will not do to say that God only uses our cancer but does not design it. What God permits, he permits for a reason. And that reason is his design. If God foresees molecular developments becoming cancer, he can stop it or not. If he does not, he has a purpose. Since he is infinitely wise, it is right to call this purpose a design. Satan is real and causes many pleasures and pains. But he is not ultimate. So when he strikes Job with boils (Job 2:7), Job attributes it ultimately to God (2:10) and the inspired writer agrees: “They . . . comforted him for all the evil that the Lord had brought upon him” (Job 42:11). If you don’t believe your cancer is designed for you by God, you will waste it.
DP: Recognizing his designing hand does not make you stoic or dishonest or artificially buoyant. Instead, the reality of God’s design elicits and channels your honest outcry to your one true Savior. God’s design invites honest speech, rather than silencing us into resignation. Consider the honesty of the Psalms, of King Hezekiah (Isaiah 38), of Habakkuk 3. These people are bluntly, believingly honest because they know that God is God and set their hopes in him. Psalm 28 teaches you passionate, direct prayer to God. He must hear you. He will hear you. He will continue to work in you and your situation. This outcry comes from your sense of need for help (28:1-2). Then name your particular troubles to God (28:3-5). You are free to personalize with your own particulars. Often in life’s ‘various trials’ (James 1:2), what you face does not exactly map on to the particulars that David or Jesus faced – but the dynamic of faith is the same. Having cast your cares on him who cares for you, then voice your joy (28:6-7): the God-given peace that is beyond understanding. Finally, because faith always works out into love, your personal need and joy will branch out into loving concern for others (28:8-9). Illness can sharpen your awareness of how thoroughly God has already and always been at work in every detail of your life.
JG: The line that strikes me today is “God’s design invites honest speech, rather than silencing us into resignation.” I’ve been resigning myself to cancer and it has silenced me before God. Is it because I don’t believe it is his design? Or perhaps I don’t believe that his design is good. This is one of those places where my thinking about God in human terms gets me all hung up. Who would ever design cancer to be a part of someone’s life? How is that love? How is that good? I am asking all the wrong questions. And my vision is from my own eyes not the perspective of God. Do you remember how God answered Job’s questions? He basically said, hey I created everything and you question me? God taught Job to fear him; he showed Job his majesty, his power, is sovereignty. After that, Job had a proper understanding of himself and of God. The fear of the Lord is the beginning of wisdom the Proverbs say. So if I want to gain wisdom about this design of cancer in my life, I must start with who God is. “The LORD, the LORD, a God merciful and gracious, slow to anger, and abounding in steadfast love and faithfulness,” (Exodus 34:6). This is my starting point, believing that God is who he says he is makes believing cancer is his good design possible. Oh, LORD, merciful, gracious, loving and faithful bring me to the place where I believe with my whole heart that this is your design. Take me from resignation and silence to honest cries of my need and joy because of who you are.
Material is from Don’t Waste Your Cancer by John Piper, copyright 2010. © Desiring God
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On the Greisen Side of Life 
Hard for me to think about what is “don’t waste your ______” in my life. But then I read this in a prayer this morning, ” I rejoice to think that all things are at thy disposal, and it delights me to leave them there.” Realized that I have been “mulling” a situation in my life rather than just leaving it there. This morning I intentionally believed in God….I cast it on Him who cares for me.
Thanks.