A.B. Simpson emphasizes the importance of recognizing and embracing the specific roles God has assigned to each believer, suggesting that many Christians struggle with feelings of inadequacy and the belief that they are not pleasing God. He encourages believers to find joy and power in their service by faithfully filling their designated places, no matter how small or seemingly insignificant. Just as every part of a machine has its purpose, so does every Christian have a role in God's plan, and by accepting this, they can contribute meaningfully to His work. Simpson reminds us that even the smallest acts of service can have a profound impact, as everyone has something to offer.