The Orchot Hatziddikim makes a very important point about human nature and knowing oneself. The Torah gives many restrictions as to how one should conduct oneself. The Rabbis often include such safeguards, as they have a good understanding of basic human weaknesses.
We are speaking here of another aspect needing emphasis. That is, there are people who have stronger than average lusts in certain areas. These people might need to take upon themselves additional fences, to keep themselves in check.
Typically, one might have a stronger than average drive when it comes to sexual urges. There could be a problem controlling anger, or the pursuit of money.
In situations such as these, one must go beyond the letter of the law, and add additional restrictions upon himself, even more than is laid down in the Torah and the Rabbis.
This involves a constant awareness of such weaknesses, and a serious desire to overcome them. This is another example of how studying books of Mussar, can help us in so many ways. Self improvement never end. We can all use help in getting there.