The pasuk says: velo sasuru acharei levavchem ve’acharei einechem. Rashi brings from chazal: the eyes are scouts for the body. The eyes see, then the heart desires, and the rest of the body gets dragged into it as well. This raises an obvious question: the pasuk says einechem only after having said levavchem. If the chazal that Rashi brings is truly the torah sheba’al peh counterpart to this pasuk; if the lesson of this pasuk is, in fact, that first the eyes see and then the heart desires, why is the order switched?
There are many answers given. The following is very close to pashut peshat, and brings home an important point.
The cycle goes as follows: A person is walking, and something provocative catches the corner of his eye. Curious, his automatic urge is to take a second glance, to turn his head, lift his eyes, and look. Says the torah: velo sasuru acharei levavchem ve’acharei einechem. We cannot control what leaks into the corner of our eye, or what pops into our direct line of vision. The ikkar is: Do not follow your heart and take a second look. Acharei levavchem, and then ve’acharei einechem. Do you know why you should not take that second glance? Because the eyes are the scouts for the body. The eye sees, and the heart wants, and leads the rest of the body to sin.
The words of the pasuk and the words of chazal/Rashi complement each other. The pasuk is telling us the prohibition - do not follow your heart to take that second look with your eyes. The corresponding chazal is warning us of what we know only too well - if you take that second look, the eyes will effect the heart, and pull the body into sin.
I think this is important for any male member of our species, especially us. It is something I am working on myself, as I have come to understand that it is truly the cornerstone to our struggle. Training ourself not to take the second glace… and feeling good about it.