Before he dies, Joshua reminds his people that, in creating them in His image, God has given them the dignity of choice. Scripture reveals a God who chooses and who creates a people who also choose. Some see a contradiction in this, but the order of things is clear from the very beginning (courtesy barlow_girl: when asked to reconcile divine predestination with human freedom, Charles Spurgeon replied, "I never reconcile friends."). Just as with every capacity God has given in His image, it is exercised with limited power under His complete sovereignty. God's choices carry His authority; our choices express the dignity He's given, to His glory.
As one whose security rests firmly on God's choice, I too often forget or neglect how important my choice to serve Him is. It matters. Joshua even knows the limits of Israel's ability to follow through on their choice (verse 19: "But Joshua said to the people, 'You are not able to serve the Lord, for He is a holy God...'"), yet the choice is still important. For me, it is all the more—since I am clothed in a righteousness not my own, I can serve this holy God freely, and I am called to do this. Yet the choice is there, and even in not making it consciously and deliberately I choose something less than Him.
Today, I am choosing better.