What they mean when an individual must have a light heart. They need a heart that is not corrupted with sin and evil intentions. The heart must be light and full of love and compassion including forgiveness. This is when Osiris the Egyptian God of the Underworld will determine if the person is fit enough to ascend into the Heavens. In Egypt the process of mummification was important because they chose which parts were good enough for the person to take with them to the Afterlife. The Heart being the most important was saved for when the judgement was to take place.
Inside of the Egyptian Book of the Dead it speaks on behalf of this Egyptian man named Ani. He is lead to the chamber of judgement. Anubis (god of mummification) brings Ani to this huge scale. Ani realizes his heart is in a jar on one side of the scale, and on the other side is a feather of the goddess Maat. Not only is Anubis here during this judgement Thoth is also here with the Book of Life that has recorded Ani's life choices, and how Ani has lived his life. Thoth is there to record the outcome of the weighing. The heart cannot only be heavy with sin or evil but also regret, unfinished Earth business, or pulls of selfish desires. If Ani had a heart such as this he would not be allowed into the Heavens. This is the reason for the soul being sent back to Earth for a light heart.
Now let me ask the question to you the reader. Do you have a light heart? Or is your heart heavy with doubts, uncertainties, unfinished Earth business etc.? This question is even asked on the Edgar Cayce website, because it is a very important question to ask. This gives rise to change that about your heart if it isn't a light heart.
Edgar Cayce a lot of you may know as the 'Sleeping Prophet'. He met an Egyptian high priest named Ra Ta. A very interesting thing about Ra Ta is that he was able to extend his life. Before Ra Ta did this he was very old and even decrepit looking. He was able to rejuvenate himself by extending his life another 100 years. He did this so he could see the construction of the Giza pyramids coming to life. Cayce asked the high priest how he extended his life to live another 100 years. Ra Ta told Cayce that he cast away the years of toil and strife things that would cause any person to age. He let it all go away and melt from his spirit.
With all of these worries a lot of us have especially today. Slowly it begins to kill us on the inside. People get too stressed out and then this leads to a heart attack, or to end up having strokes. We should keep our spirits in balance, and make sure no struggles we have been through bother us. We just push it from our lives like it never even happened. Yes it may creep up every once in a while, but the learning process is to not let it get to us. I went through a family death to someone who was very dear to me. It does hurt to talk about. It hurts they are gone. But I do know they are a spirit and no longer have to feel pain.It may take me a while to get use to that concept. I will have to get use to it I guess.
Here is the link if you want to read more into the Egyptian Judgement. Also learn more about Edgar Cayce and the readings he has performed. People have discredited his readings out of spite. Cayce has experienced more than any other person has.