The "Book of the Dead" was a survival guide for ancient Egyptians. It was to guide them safely on the journey they would take from death, through the dangers of the Underworld to the Afterlife; the Egyptian version of what we call Heaven. The Afterlife was seen as a perfect existence in an ideal version of Egypt.
In order to get there however, they would need to pass the "Ceremony of Justification." Entering the Hall of Truths, they would find a balance scale. On one side of the balance scale a feather would be placed. And on the other side, their heart. In order to enter the Afterlife, the heart would need to be lighter than the feather. If they did not pass the test, they would lose their heart, that would be the end of them.
Some say the Book of the Dead is myth, others say it is secrets and mysteries. Looking at it from the spiritual perspective, one can see the "thread of Truth;" Spiritual Principle that runs through it, as well as the beliefs of just about all religions.
"Truth" is that which is absolute, eternal and unchanging. Nobody has "exclusive rights" on that. God is absolute, eternal, unchanging, "non-denominational Spirit" that we have given many names and attributes. Our various understandings about "truth" are filtered through our mind, experience, and the religious framework we have learned throughout our lives.
The heart, in our Judeo-Christian tradition, plays a critical part. In fact it is noted in the Bible 1018 times. The terms 'heart' and 'mind' had a central meaning that made them interchangeable, both meaning the combined thinking and feeling nature and processes.
The combined thinking and feeling nature and processes are also central to what we call the "Creative Process;" thought+feeling=manifestation. So, if we put our current state of consciousness; our "heart" on the scale, how heavy would it be? It does not take a theologian or rocket scientist to figure out that we cannot get to heaven; to uplifted, enLIGHTened consciousness with a heavy heart.
A long-term heavy heart consciousness can have dramatic negative effects on our lives, the lives of those we love, and the world we live in. We certainly don't want to "lose heart," and access to a hereafter..."here" or "there;" now, or later...of abundant good.
Want to get to heaven? Lighten up! 
