Passage
And it shall be, if thou shalt forget Jehovah thy God, and walk after other gods, and serve them, and worship them, I testify against you this day that ye shall surely perish.
And it shall be, if thou shalt forget Jehovah thy God, and walk after other gods, and serve them, and worship them, I testify against you this day that ye shall surely perish.
Deuteronomy 8:17 and [lest] thou say in thy heart, My power and the might of my hand hath gotten me this wealth.
Deuteronomy 8:18 But thou shalt remember Jehovah thy God, for it is he that giveth thee power to get wealth; that he may establish his covenant which he sware unto thy fathers, as at this day.
Deuteronomy 8:19 And it shall be, if thou shalt forget Jehovah thy God, and walk after other gods, and serve them, and worship them, I testify against you this day that ye shall surely perish.
Deuteronomy 8:20 As the nations that Jehovah maketh to perish before you, so shall ye perish; because ye would not hearken unto the voice of Jehovah your God.
The verse centers on "shall", "thou", "shalt", "forget", "jehovah", "walk", "after", and "other". It is saying that the verse draws attention to "shall" and "thou", so its meaning should be read from those terms before moving to application.
The nearby context moves from verse 18's "But thou shalt remember Jehovah thy God..." into verse 20's "As the nations that Jehovah maketh to...", so "shall" and "thou" belong inside that flow. In Deuteronomy context, the local focus is covenant, worship, and faithfulness.
A plain takeaway is to answer the verse's own emphasis on "shall" and "thou" with trust shaped by these words, not by a vague optimism outside the passage.