Dallas Willard, in Hearing God, writes: "Spiritual Formation into Christlikeness - true change of character - comes from living in relationship to God." (29)
Willard's statement is not just a string of words to me; the truth of this statement is not mere theory. I know these words, in experience. Experiential truth is more powerful, vastly so, than theoretical truth. This is truth that happens, and ongoingly so.
In addition to personally knowing this to be true, I know its truth from my vantage point as a pastor and teacher. I have seen it in many people. A significant stream of former seminary students write me of their ongoing experiential, conversational relationship with God, in Christ, and by the Spirit.
Willard quotes 19th-century theologian Wilhelm Hermann:
“We hold a man to be really a Christian when we believe we have ample evidence that God has revealed himself to him in Jesus Christ, and that now the man’s inner life is taking on a new character through his communion with the God who is thus manifest.” (p. 29) I know many real Jesus-followers. We have a "knowledge of God [that] rests on the revelation of his personal presence. . . . Of such a presence it must be true that to those who have never been confronted with it argument is useless, while to those who have, it is superfluous [more than enough].” (Ib.)
Live consistently in God's presence and you will become familiar with the sound of his voice.