The Ramchal in Derech Hashem lays out our purpose in life. We are born with a primarily self-centered orientation and our mission is to transform ourselves into Hashem-centered people. Improving our character traits (middos) helps us break our self-centered orientation, while doing mitzvos helps us develop a Hashem-centered orientation.
From Rosh Hoshana thru Yom Kippur, since Hashem, Our King, is so prominent, we can accomplish more in the way of Hashem-centeredness. To really take advantage of this we need to break our self-centeredness through middos development.
In the Mesillas Yesharim, the Ramchal lists the four middos which need the most work: Pride, Anger, Envy and Desire for honor and money. All these middos involve other people, and we need to turn down the volume on our perspective and turn up the volume on the other person’s perspective. To the degree we do this and diminsh our self-centerness, is the degree to which we can make Hashem our King and the central force in our lives.
The people we meet in Shul give us many opportunities to diminish our self-centeredness and make Hashem and His mitzvos the focus of our lives. Elul is a great time to take advantage of these opportunities as we travel from Me to Hashem Via You.