Thomas Brooks emphasizes the profound anger that true penitents feel towards their own sins, illustrating that this self-directed anger is far greater than any frustration they may have towards others or external circumstances. He argues that genuine repentance involves a deep loathing and abhorrence of sin, which should be the primary focus of a believer's indignation. Brooks encourages believers to redirect their anger away from others and towards their own sinful actions, highlighting that true anger should be reserved for sin itself, not for disagreements with fellow believers.