Musar zu Schoftim 14:3

Commandment 387 is not to follow the inclination of one's eyes or heart, since the Torah commands in 15,39: "so that you do not follow the inclinations of your eyes or your heart which you are in the habit of following after. This prohibition concerns our not adopting attitudes that are at variance with Torah principles. Once one concentrates on such ideas, one easily errs in one's practice also. The moment one feels persuaded by such alien ideas one must desist from pursuing them, and change back to contemplate what Torah views are on the subject matter concerned. It amounts to a warning not to pursue desires that are of a transient nature if fulfilled and which are bound to lead one to an unhappy end. This is what our sages had in mind when they said that the meaning of the words "after your hearts," is not to pursue heresy. The meaning of "after your eyes" is not to indulge in sexual licentiousness (Berachot 12b). We have an allusion to this when the book of Judges 14,3, says of Samson "he said to his father: "take this one for me for she is good in my eyes."