The essence of lukewarmness is the statement, “I need nothing.” The lukewarm are spiritually self-satisfied. To find out whether you are among that number, don’t look into your head to see if you think that you are needy; rather, look at your prayer life. It doesn’t matter what we think in our head, the test of whether we are in bondage to spiritual self-satisfaction is how earnest and frequent and extended our prayers for change are. Do you seek the Lord earnestly and often in secret for deeper knowledge of Christ, for greater earnestness in prayer, for more boldness in witness, for sweeter joy in the Holy Spirit, for deeper sorrow for sin, for warmer compassion for the lost, for more divine power to love? Or is the coolness and perfunctoriness of your prayer life Exhibit A that you are spiritually self-satisfied and lukewarm? – John Piper