Joshua 11:23 shows us the faithful fulfillment of the promise: the land was taken, divided among the tribes, and the land experienced rest from the battles. God accomplished through leadership and communal effort what He had commanded Moses; the victory belonged to the Lord and the inheritance was granted to the people.
As Redpath observes, much territory remained to be truly possessed — not for lack of divine power, but because each tribe had to apply, individually, the lessons learned in the common war. In Christ something similar happens: the victory has already been won by Jesus and the inheritance is promised, but each believer is called to, in faith and obedience, take possession of what has been given to them.
In pastoral practice this means clearly identifying the portion assigned to you — your calling, gifts and responsibilities — and applying the lessons learned in the community: persevering in the Word, in prayer, confronting sin with repentance and acting faithfully in service. The church can fight alongside you, but effective possession requires concrete decisions, small daily obediences and the courage to press forward against personal resistance.
When the people finally took their portion, the land enjoyed rest; likewise the peace and rest promised in Christ are manifested when we claim and keep our inheritance in obedience. Do not expect someone else to take for you what the Lord has already given you: move forward, take possession and rest in the victory of Jesus. Courage — the Lord has already won; now go and live the inheritance He has given you.