Making the most out of his cultivation technique involved more than just deciding to do better. The nameless technique he was now cultivating was similar to Regal Embrace in the regard that it could adapt tremendously and had no upper limit. Unlike the Regal Embrace, however, it would not run into a problem where growing further could lead to death.
It was also extremely intuitive. For example, the moment Lex decided his goal of surpassing Regal Embrace and Mo's Blessing, the cultivation technique adapted automatically and informed him of what he needed to do to proceed.
As it turned out, cultivating the most powerful cultivation technique in the universe was extremely resource intensive. On his defensive front there was not much work needed, as Regal Embrace had built an adequate foundation for him to proceed from. The issue was his body's attack capabilities. He was severely lacking in them.