Darash Chai - Seek Life!

Yom Kippur is a day that is unlike any other. It is the Day when atonement was accomplished in the Hebrew Scriptures, and it was on this day that the sins of the people were dealt with. But there is one instruction that is attached to this day that is not explicit in its meaning. The command to "afflict your soul" is one that could have any number of meanings and purposes. What does it mean to "ve'innitem et nephshotechem?" and why is this instruction attached to this day of cleansing?