The Great Dao of Heaven and Earth was the most obscure and difficult to understand. This was something that everyone knew.
Below the Divine Abilities Stage, there was no question of comprehending the Dao. It was basically a process of continuously strengthening one's physical body. For dual cultivation of life and death, the physical body was the foundation of everything below the Divine Abilities Stage. It was the most important.
In the endless sea of bitter cultivation, only when the body was strong enough could it transform into a small boat that carried the cultivator to the other side of cultivation.
However, when one reached the Divine Abilities Stage, one had to begin strengthening their spiritual cultivation base to comprehend the Heavenly Dao. However, the Heavenly Dao was so obscure and difficult to understand.