The Portion of Ki Tavo has two main themes. It talks about the blessings which will be heaped on the Jewish people if they follow the laws of the Torah and it also warns, in what is known as the תוכחה, of the tragic consequences of disobeying the Torah. One particular verse stands out.
Moshe says to the people, “Hashem will confirm you for Himself as a holy people, as He swore to you” כִּי תִשְׁמֹר אֶת מִצְוֹת יְקֹוָק אֱלֹקֶיךָ וְהָלַכְתָּ בִּדְרָכָיו, “if you observe the commandments of Hashem your God and you go in his ways.” (Deut. 28,9) We don’t become a holy people of Hashem automatically. It is contingent on conforming to His ways.
The העמק דבר, the Biblical commentary of the Netziv, makes a very pertinent comment on this verse. A person who may desire to become holy may decide his best way is to set himself aside from worldly life, and so doing, avoid performing certain Mitzvot that relate to daily living that may interfere with his holy state. To such a person, the Netziv claims, Moshe speaks and says, if you want to be holy you must observe all the Mitzvot, whether they pertain to heavenly obligations of simply responsibilities to your fellow man.
In short, holiness in Judaism is not setting yourself above daily life and avoiding contact with others but rather living with people and acting towards them in the way the Torah prescribes.