Our Gemara on Amud Aleph discusses the change in liability of an animal that already had been exposed to food that it ate after falling into a garden.  Even if ordinarily the owner might be exempted from paying for what the animal eats if he took ordinary and reasonable measures to prevent it from breaking into another’s property, if this animal comes back to this garden, the owner will still be liable.  The Gemara says that since the animal was already exposed to this garden and knows where the goodies are, its owner has to take extra steps to watch and prevent the animal from breaking in again.  As we have seen in a number of previous dappim, human nature and animal nature have many parallels, because aside from our very large brains, underneath we also have an instinctive animal side.  As it states in Koheles (3:19), “Man has no superiority over beast, for all is comparatively vapor.” Humans, like animals, have a difficult time resisting a sinful behavior once they have been exposed.  

Gemara Yoma (86b) warns:

כֵּיוָן שֶׁעָבַר אָדָם עֲבֵירָה וְשָׁנָה בָּהּ…נַעֲשֵׂית לוֹ כְּהֶיתֵּר

When a person commits a transgression and repeats it…it becomes to him as if it were permitted.

How do we counter this nature?  Rav Yisrael Salanter offers two suggestions in two different sections of Ohr Yisrael (Iggeres Hamussar 22 and Kokhvei Ohr 7).  In Iggeres Hamussar he advises that one continuously learn the halakhos pertaining to the area where he is tempted to sin.  The study of the matter leads to reinforcing the seriousness and significance of the matter. In addition, in Kokhvei Ohr he says the part of repentance that focuses on regret is designed to re-establish the boundary and the sense of how terrible it was to violate it. While our feelings are notoriously difficult to change, and especially if we are exposed and succumb to something that tempts us, the temptation becomes stronger. However, difficult is not impossible, and Rav Yisroel’s advice is a great tool, though do not expect immediate results.