The Rambam is warning that promiscuity begins with gazing at women who are forbidden to you. Even though a man may rationalize that he is above such behavior, the Rambam informs him that self-control must start at the beginning. Controlling our eyes from looking at women is the most powerful preventative . Like a loving parent who sets limits on his children for their own safety, the Torah instructs us not to look at women for our own spiritual and physical well-being.
You might be wondering: how can a man live in the world without seeing immodestly dressed women? Isn't it inevitable that every time he steps into any public area his eyes will take in everything?
The fact is that we are required to avoid looking at immodestly dressed women and images, and to develop an aversion to looking. As long as one follows these two stipulations, even if he inadvertently sees, he is not culpable. But after inadvertently seeing, he must turn his eyes away. If he continues looking or takes a second look, he commits the aveirah of "straying after his eyes."
Today: Resolve to practice the laws of Shmirat Einayim for your own protection and to enhance your marriage.