O, the triviality! Flee from the triviality!

Of course, we do not use the word cool to describe true greatness. It is a small word. That’s the point. It’s cheap. And it’s what millions of young people live for. Who confronts them with urgency and tears? Who pleads with them not to waste their lives? Who takes them by the collar, so to speak, and loves them enough to show them a life so radical and so real and so costly and Christ-saturated that they feel the emptiness and triviality of their CD collection and their pointless conversations about passing celebrities? Who will waken what lies latent in their souls, untapped—a longing not to waste their lives? 

Oh, that young and old would turn off the television, take a long walk, and dream about feats of courage for a cause ten thousand times more important than American democracy—as precious as that is. If we would dream and if we would pray, would not God answer? Would he withhold from us a life of joyful love and mercy and sacrifice that magnifies Christ and makes people glad in God? I plead with you, as I pray for myself, set your face like flint to join Jesus on the Calvary road. “Let us go to him outside the camp and bear the reproach he endured. For here we have no lasting city, but we seek the city that is to come” (Hebrews 13:13-14). When they see our sacrificial love—radiant with joy—will they not say, “Christ is great”? 

 -pp. 128-129 from Don't Waste Your Life by John Piper

Oh, you precious soul! Flee from the triviality of this age, and live to display what is truly significant, the glory of God through Jesus Christ!

Wasting life by simply avoiding badness and providing for the family

Oh, how many lives are wasted by people who believe that the Christian life means simply avoiding badness and providing for the family. So there is no adultery, no stealing, no killing, no embezzlement, no fraud—just lots of hard work during the day, and lots of TV and PG-13 videos in the evening (during quality family time), and lots of fun stuff on the weekend—woven around church (mostly). This is life for millions of people. Wasted life. We were created for more, far more.
 - p.119-120, Don't Waste Your Life by John Piper

To be happy and to be holy, now and hereafter

Now it is here demonstrated by eternal truth itself, that it is our interest to be religious; and therefore religion deserves to be called wisdom, because it teaches us to do well for ourselves: and it is certain, that the way to be happy, that is perfectly holy, hereafter, is to be holy, that is, truly happy, now. It is laid down for a principle here, 'Happy is the man that findeth wisdom' (Prov. 3:13) that finds the principles and habits of it planted in his own soul by divine grace;
 -- p. 23, The Pleasantness of a Religious Life by Matthew Henry (or original page 5-6)

Taking risks for the sake of God's Name.

And now what about you? Are you caught in the enchantment of security, paralyzed from taking any risks for the cause of God? Or have you been freed by the power of the Holy Spirit from the mirage of Egyptian safety and comfort? Do you men ever say with Joab, “For the sake of the name, I’ll try it! And may the Lord do what seems good to him”? Do you women ever say with Esther, “For the sake of Christ, I’ll try it! And if I perish, I perish”? 

There is more than one danger in calling Christians to take risks. I mentioned one of them in Chapter 4, namely, that we might become so fixated on self-denial that we are unable to enjoy the proper pleasures of this life that God has given for our good. Another danger, which is worse, is that we might be drawn to a life of risk for self-exalting reasons. We might feel the adrenaline of heroism rising. We might scorn the lazy and cowardly and feel superior. We might think of risk as a kind of righteousness that makes us acceptable to God. What would be missing from all these mistakes is childlike faith in the sovereign rule of God in the world and in his triumphant love. 

I have been assuming that the power and the motive behind taking risks for the cause of God is not heroism, or the lust for adventure, or the courage of self-reliance, or the need to earn God’s good will, but rather faith in the all-providing, all-ruling, all-satisfying Son of God, Jesus Christ. The strength to risk losing face for the sake of Christ is the faith that God’s love will lift up your face in the end and vindicate your cause. The strength to risk losing money for the cause of the Gospel is the faith that we have a treasure in the heavens that cannot fail. The strength to risk losing life in this world is faith in the promise that he who loses his life in this world will save it for the age to come.

  - pp.89-90 from Don't Waste Your Life by John Piper (emphasis mine)