When you go down into the Underworld (Hell), demons will come to try to satisfy your wants. The only way to get out of the trap is to want nothing, not fame, fortune, sex, food, etc.

It's a giant interconnected prison filled with hallways where the try to get you to reincarnate back up here. The only way out is to want nothing material or selfish.

This is also described similarly in traditional Gnostic texts, where the Archons hold your soul back from ascending depending on your soul's material wants.

The physical body can't remain youthful because it's made out of material, dirt, affected by gravity pulling it down into the ground, because the dirt you're made out of wants to get back to its source: the soil. Recognition of the divine spark and "Pneuma" can extend your life, however.