The sermon focuses on Psalm 71, highlighting the theme of trusting in God and not one's own understanding, particularly in times of struggle and old age. Pastor Ben emphasizes the importance of continually hoping in and praising God, even when facing adversity, and proclaiming God's righteousness rather than one's own. The sermon encourages the audience to reflect on God's faithfulness and the "mighty acts" He has done in their lives, trusting in His sovereignty even when life presents challenges.