Why Prepare?

I am in complete agreement with Burroughs when he says we must prepare ourselves for worship.  I immediately think of the humility of Isaiah when he realizes he is in the presence of God.  Isaiah cries,“Woe to me!  I am ruined! For I am a man of unclean lips, and I live among a people of unclean lips, and my eyes have seen the King, the Lord Almighty.” (Isaiah 6:5)  How I pray that I might recognize this truth when I too come into God's house.  In our culture I find that we emphasize the idea of Jesus being our close friend to such a degree that God's awesomeness and our fear of Him has been undermined.  We must approach God with trembling.  But, Isaiah is cleansed and then is able to say,“Here am I. Send me!”  This too should be a passion of our hearts as we see God.  I pose the question if we have the Holy Spirit living and working in us, for what purpose should we prepare?  I am not saying at all that preparation is unnecessary or unimportant.  What I am saying is this, if God views me no longer bound to the flesh, but through the blood of His Son, Jesus Christ, and with the indwelling of the Holy Spirit, is it for my benefit that I focus on cleansing, or for God's?  Is the main reason that I benefit from preparation, because I will be able to better worship with a clean heart and draw closer to God?  Or is the main reason, so that God can receive more glory through me?  Also, if there is any genuine pleasing of God, is it not the Holy Spirit at work and not myself?  How should I go about allowing my soul to be cleansed before I approach the throne of God, and for who's benefit, and for what purpose is this preparation?