This week's Torah portion starts with the words "When you go out to war upon your enemies..." In addition to the literal meaning, this verse is also understood to be speaking of the ongoing, internal battles being waged in our hearts and minds between our inherent good and evil inclinations.
If you want to succeed in this internal battle, as is true in any battle, first and foremost you must go out with an attitude of "upon" your enemies. Which means that you must firmly believe in the righteousness of your cause and be confident in your ability to win.
With that attitude, you have the first step to assuring a complete victory.
Shabbat Shalom,
Rabbi Yitzi Schmukler