John Nelson Darby addresses the struggle with unbidden and hated evil thoughts that arise even when one is focused on the Lord. He emphasizes the need for deliverance from the flesh and encourages believers to recognize that these thoughts do not define them. Instead of stopping to confess these thoughts, Darby advises to ignore them and continue in communion with God, as acknowledging them only gives power to the flesh. He reassures that this experience is common among believers and encourages a focus on God's strength in moments of weakness.