The Jews today take Deuteronomy 6:8, 9 very literally, and inscribe Deuteronomy 6:4 in a box on all their doorposts and gates, as well as often wearing a small box on their foreheads and hands. While this is not a wrong way to read the text, and certainly would remind you very visibly of your relationship with God, it is also not all that the text entails, as explained above in verses 6–9. By thinking and talking of God’s word and your love relationship with Him all day long, and acting in accordance with it in all you do and with all you own, you are truly living out this life of love for God. This is necessary because we are prone to forget all that God has done for us and ascribe it to our own talents and work. Moses warns Israel of this in verses 10–15. God is the one who gives blessings and delivers them, but the temptation is to forget Him and to tempt Him, rather than following in His ways out of gratitude and love.
As we have seen in previous passages in Deuteronomy, God is a jealous lover and longs to keep growing in intimacy with His people. It is important to realize that God would not act vindictively to end His relationship with the people, but rather act in the passion and anguish of unrequited love (v. 14). He had saved them miraculously so many times, and yet they have continued to turn from Him over and over. And as we see with many other nations, if people repent, God is always willing to save those people, even if the nation as a whole is totally given over to evil and utterly refuses to repent (Gen. 6–9; Josh. 2; Amos 9).
In addition, this is not a prosperity gospel, which teaches that if you obey, God will bless you, but if you do not obey, you will experience bad things. However, there is some truth to the idea of a prosperity gospel simply because following God’s laws is actually what is good for us, bringing health and freedom and joy. So when we don’t follow His laws, there are natural and logical consequences that come our way, including disease, addiction, and sadness. But it is not that God is delighting to destroy us; it is that we are destroying ourselves, while God is trying to save us and bring us back to the way that will bring us most joy and eternal fulfillment. Of course, there are times when punishments come, by God allowing other nations to intervene, but these are always meant to be redemptive as well, until the final punishment when everyone not following God is totally given over to evil and there is no way God can reach them anymore (Gen. 6; Revelation).