@donkeypong, That's another biggest learning part no two blog. I love and prefer to find historical things like as Greek and Egypt history. Some of Pyramids in Egypt has hidden mystery stories. Lot of movies created like Mummy.
I heard before some of Middle Ages stories. But don't know everything. I learnt something of Prester John before and very interesting statement he told and you mentioned it nicely here.

He said he ruled over the Amazons and other people, that he was wealthy, that no one in his kingdom ever sinned, and that he had a watch tower manned by 3000 men which could see into every part of his kingdom.

Look at above. How about his thought and believe of him. Peoples believe about himself better rule. But how they believe Immortality? Lot of contents came from their religious leaders and Dictatorship. And they totally think they're legends then need to stay live everyday. Another interesting story created Juan Ponce De Leon. You mentioned better about him.

Today, there is a major push toward extending human life. Billionaires are financing projects with particular potential for attacking limiting factors such as cancer.

Of course, we can see it from current society. But with some technological & chemical products not deserve to our body everyday. Need maintain everyday.
I think better solution is keep your mindset and brain very clearly and positively. Then you don't need to be sad forever. Thanks your Top class blogs Tom.