After entering intermediate Nascent God Level 3, Mo Wuji knew what went wrong with him: his heart state was misaligned.
As he grew stronger, the people that interacted with him also became stronger. This made him want to increase his cultivation level at a crazy rate. Since he entered the God Domain, he had reached Nascent God Level 3 in a short period of time.
This was at odds with the foundation of his cultivation technique, as he was cultivating as a mortal. However in the process of cultivation, he had continuously compared himself to those cultivation geniuses and as a result, unknowingly considered himself as a true cultivation genius as well. It was already very lucky that he did not go astray in cultivation under such circumstances, what more for advancing in cultivation level?
