From The Hidden Smile of God by John Piper:

The fruit of William Cowper’s affliction is a call to free ourselves from trite and chipper worship. If the Christian life has become the path of ease and fun in the modern West, then corporate worship is the place of increasing entertainment. The problem is not a battle between contemporary worship music and hymns; the problem is that there aren’t enough martyrs during the week. If no solders are perishing, what you want on a Sunday is Bob Hope and some pretty girls, not the army chaplain and a surgeon.
   Cowper was sick. But in his sickness he saw things that we so desperately need to see. He saw hell. And sometimes he saw heaven. He knew terror. And sometimes he know ecstasy. When I stand to welcome the people to worship on Sunday morning, I know that there are William Cowpers in the congregation. There are spouses who can barely talk. There are sullen teenagers living double lives at home and school. There are widows who still feel the amputation of a fifty-year partner,. There are single people who have not been hugged for twenty years. There are men in the prime of their lives with cancer. There are moms who have risked all for Jesus and bear the scars. There are tired and discouraged and lonely struggles. Shall we come to them with a joke?
   They can read the comics every day. What they need from me is not more bouncy, frisky smiles and stories. What they need is a kind of a joyful earnestness that makes the broken heart feel hopeful and helps the ones who are drunk with trifles sober up for greater joys.

—John Piper, The Hidden Smile of God, 167.