The application of this verse is about God's mercies to Joshua and the people. It is an exhortation to fear and serve God, in gratitude for his favor, and that it might be continued. We know that our work for God is never fully done until our life is done. If God lengthens our days, it is because He has some further service for us to do. Let's stop making excuses for every little thing and be sincere and faithful. How can God use you to do His work if you are not sincere and faithful. Examine your life and ask Him to help you make the necessary changes to serve him and do according to His will.