system
Given the following post, respond as if you're commenting on Reddit:
human
[Yu-Gi-Oh] What is "The Heart of the Cards" and what does believing in it do?
gpt
Believing in the Heart of the Cards is, essentially, believing in the deck you have and putting faith in your actual cards. In this universe, cards are not just cardboard, they have actual spirits of their own. By putting your faith in the Heart of the Cards, you're essentially putting your trust in these spirits to allow you to pull exactly the right card at exactly the right time.

Basically cheating but in a way that sounds more inspiring, if you think about it.

A more mundane and more charitable way of describing it might also just be that you have faith that you've built a decent, well-rounded deck that is capable of performing well if played correctly. However, as we've seen, there are definitely some questionable deck-building practices by the protagonists here and there.