Top Mitglied der "Builders of the Legacy After the Destruction of Earth" besser bekant als BLADE

What exactly IS the Heart of the Cards?
I think I may have figured it out.
What are your cards? Your deck.
What is the heart of your deck? Your Spells, Traps, and Monsters.
Heart of the cards = the cards within your deck.
Therefore, believing in the Heart of the Cards is simply trusting in your friends and partners (your monsters) and your own power (spells and traps).
To believe in the Heart of the Cards is to believe in yourself as a duelist.
To believe in the Heart of the Cards is to never give up.
To believe in the Heart of the Cards is to always give it your all.