The soul we have is the life that God himself has breathed into us. He has a mind, emotions, and decision making ability just as we do. From this, several important conclusions can be made.
First, because God is a Person, as we are (yes He is so much more than we and beyond comparison, yet He humbles Himself to reach out to us ) we can conclude this: we can know Him, person to Person. Our spirit can know His Spirit just as your spirit can know mine.
Second, because the above is in fact true, then it follows that when we are truly converted by believing in Christ, that He makes Himself known to us. He puts His name on us. Thus, not only are we His, He has made Himself to be ours. That is true because whatever we put our name on becomes our responsibility in some way. Thus, that which bears our name has a call upon our response. Since He has put His name on us, He has made Himself available to us.
Finally, since He is greater than the world, His victories over the world are available to us. By faith, we see that Satan presents himself as an invincible fortress. But, by faith we see through Christ's eyes that Satan is a liar. He is only a dark cloud of deception. God, our Father would has a father's heart, is the fortress. And, He has placed us in it, if and only if we are truly His.