What is the moral message in The Strange Case of Dr. Jekyll and Mr. Hyde by Robert Louis Stevenson?

One moral message of The Strange Case of Dr. Jekyll and Mr. Hyde is that it is necessary for the individual to wrestle with his or her own dark side; there is no shortcut or easy way to escape having to do this.  When Dr. Jekyll tries to separate his dark side, the side of him that wants to engage in immoral or unethical behavior, from his good side, he finds that -- over time -- he begins to lose control over the evil part of himself.  It becomes more and more powerful, and he can no longer fight it successfully.  He had been hoping to destroy this side of himself and find an easy way to avoid having to struggle with it.  He learns, too late, that the struggle would have been far better than attempting to rid himself entirely of the darkness.  This makes it seem as though such darkness is actually a fundamental part of every individual and that there is value in learning to control one's sinful or evil impulses.