According to Jekyll, what begins to happen to the balance of his nature? Which side begins to win? What is the symbolic interpretation for this change?

One night, Jekyll transformed into Hyde involuntarily, while sleeping. Suddenly, Jekyll realized that he was in great danger of being trapped in the body of Hyde permanently, and that some aspect of the experiment had moved beyond his control. For two months entire months, Jekyll lived only as himself. However, he soon felt the need to free his evil side, and in a moment of extreme weakness, took the potion.