"To conduct oneself properly in matters that are permitted is still fairly straightforward.
To do so with a degree of holiness is another matter.
One can be a scoundrel even within the bounds of the legally permitted in Torah, as the medieval Sage,the Ramban,said.
It is a matter of how one eats and drinks, how one goes about one’s affairs, even in the most intimate of life’s details where, in fact, the temptations are the greatest and the failures most common.
The struggles here, as the Sages have frequently noted, are real battles of life, and the need to be careful and circumspect cannot be overstated.
There are transgressions that are so intrinsically habitual that they are no longer considered sinful.
The repetition makes them commonplace and acceptable.
What is shockingly bad the first time is no longer even perceived the tenth or twentieth time."
From Pebbles of Wisdom from Rabbi Adin Steinsaltz (forthcoming)