Greg Hubbard shares a message on the concept of thankfulness as a powerful weapon for believers, drawing on Psalm 103 and other scripture passages to illustrate how gratitude can shift focus from negative circumstances to God's goodness, bring emotional resilience, and strengthen relationships. He encourages us to actively stir up a spirit of thankfulness in all situations, promoting peace, contentment, and a deeper connection with God, while emphasizing that thankfulness is a commandment and a key component in experiencing God's presence and blessings.