5"The LORD your God will bring you into the land which your fathers possessed, and you shall possess it; and He will prosper you and multiply you more than your fathers.
6"Moreover the LORD your God will circumcise your heart and the heart of your descendants, to love the LORD your God with all your heart and with all your soul, so that you may live.
The obvious encouragement from Deuteronomy 30 is the fact that God is a God of restoration. Judgment is not the final answer, even for those who have chosen poorly and have received the just consequences. God provided for restoration of the nation in the Old Testament if they would repent and return to God during their lifetime.
In addition, God foreshadowed a time when the very heart of man would be permanently changed (circumcised) and result in a people who are impelled from that new heart to fully love God and live. This time became a reality 50 days after Jesus rose again at Pentecost when God gave the indwelling Spirit to believers in the gospel of Christ.
Even though I still live in the flesh and have all sorts of sinful thoughts and actions every day, the knowledge that the core of me is pure, eternal and always and only wants to obey God keeps me full of hope. I am grateful for the Spirit who makes me uncomfortable in my sin patterns and slowly but surely overcomes those things as I give them to Him. Meanwhile, I long for that day when my flesh will go away (either by death or rapture) and my heart and my new glorified body will never be in conflict! That will be a time of ultimate peace and joy. And along with that inner peace comes the presence of God and His precious people!