Why is understanding our hearts so important in our religion? The following may give one a clue:
(Ichiretsu wa) (mina meme no) (mune no uchi)
(Hokori ippai) (tsumori aru kara) 8-61
Everyone, all of each of your innermost hearts
piles of dust have accumulated.
Kono michi o shinjitsu omou koto naraba
mune no uchi yori yorozu shiyan se 2-15
This path, if you truly think about it.
From what comes from the innermost heart, all ponder.
It appears that our fate comes from our hearts. We reap what we have sowed because of our own hearts. Our hearts collect our demerits from acting on our evil thoughts. This is why God tells us to ponder our own minds, when suffering is delivered by our own hearts. This is the way to purify our own minds. When our minds become purified, our hearts will only bring upon positive fate, a joyous life.
Heaven's Truths, in Living the Joyous Life 