More on Holiness

Ramban disagrees slightly with Rashi.  Holiness is not only about keeping yourself separate form forbidden sexual relationships.  Here are some of his comments on Lev. 19:1-2:

In my opinion, [holiness] does not refer to keeeping 'separate' from the sexual trangressions, as Rashi thinks, but to the separateness ascribed throughout the Talmud to people it calls 'Pharisees,' that is, 'Separatists,' meaning those who exercise self-restraint.  You see, the Torah proscribes man and wife, eating meat, and drinking wine.  So there is license for a man of appetite to steep himself in lust with his wife (or his many wifes), or to 'be of those who guzzle wine, or glut themselves on meat' (Prov. 23:20), or to discuss all sorts of vile things, as long as they involve something that the Torah does not explicitly prohibit.  One could therefore be a scoundrel with the full permission of the Torah. [emphasis is mine] 

And now Rabbi Louis Jacob's commentary on the Ramban's commentary (don't you love Jewish learning?  We have commentary on commentary.):

Holiness, according to Nahmanides, and he is followed by other Jewish teachers, is the attitude of the Jew who has no wish, in his pungent expression, to be “a scoundrel with the full permission of the Torah.” Nahmanides’ point is that the rules and regulations of the Torah constitute the bare minimum of decent behavior expected of every Jew, a standard below which none should fall. But an essential part of the Torah discipline is that the Jew is obliged to go beyond these minimum rules. For this there can be no hard-and-fast rules, since all depends on individual character and temperament. What may be modbid indulgence, leading to a softening of the moral fiber, for one, may be a necessity for another. For all its insistence on rules, Judaism, according to Nahmanides, acknowledges that there is a whole area of life, the area of the licit, where man’s freedom of choice must operate in determining those things which will help him to live more worthily and those which can pollute his soul.

So, according to the Ramban, if one followed Rashi's definition of holiness, one could be striving to be holy like God is holy, and still be a jerk.  For the Ramban, holiness is an ongoing process of self discipline and refinement.