The principle of Taoism states that Yin is Yin and Yang, and Yang is Yin and Yang, but each one are not balanced (Yin is a large yin and a small yang, while Yang is a large Yang and a small Yin). When these two complementary forces cooperates, the true balance can be achieved...
This is quite the same thing that appears in the Uchiha tablet.
Yang = Body = Embodiment.

that's the trick behind my theory:
When the Sage separated the Juubi in 10 parts, he created Nine Tailed Beasts and The Embodiment, with the "Creation of All Things" Jutsu.
The beasts were the Yin (large Yin and smaller Yang), Gedou Mazou the Yang (large Yang and smaller Yin).
- The reason the beasts can only be sealed inside people with a strong lifeforce is because the beasts are mainly Yin entities, and their purpose is to reach balance.
- The reason a Jinchuuriki dies when the beast is extracted is because when the beast leaves the embodiment, the lifeforce is extracted too due the beast tending to mantain balance.
- This explains too why the Uzumaki Clan was living in a village known as the Village of Longetivity, Uzushiogakure... the people had way too high lifeforce. Mito and Kushina survived the extraction of Kurama, and each time Kurama was extracted, Kurama's Yang Energy Increased since it was extracted from it's previous Jinchuuriki.
- The Yang half of Kurama (the result of two extractions, from Kushina and Mito) was inserted in Naruto, so Naruto's growth exceeded in Yang abilities. The unbalance induced too a lack on his Yin abilities.
Take a breath and analyze this theory. You'll notice that it is consistent with the events that have been happening since the start of the manga.