in loving Jehovah thy God, in hearkening to his voice, and in cleaving to him for this is thy life and the length of thy days that thou mayest dwell in the land which Jehovah swore unto thy fathers, to Abraham, to Isaac, and to Jacob, to give them.
Deuteronomy 30:18 I denounce unto you this day that ye shall surely perish; ye shall not prolong your days upon the land whereunto thou passest over the Jordan to possess it.
Deuteronomy 30:19 I call heaven and earth to witness this day against you: life and death have I set before you, blessing and cursing: choose then life, that thou mayest live, thou and thy seed,
Deuteronomy 30:20 in loving Jehovah thy God, in hearkening to his voice, and in cleaving to him for this is thy life and the length of thy days that thou mayest dwell in the land which Jehovah swore unto thy fathers, to Abraham, to Isaac, and to Jacob, to give them.
The verse centers on "loving", "jehovah", "hearkening", "voice", "cleaving", "life", "length", and "days". It is saying that the verse draws attention to "loving" and "jehovah", so its meaning should be read from those terms before moving to application.
The prior verse says "I call heaven and earth to witness...", giving immediate footing for "loving" and "jehovah". In Deuteronomy context, the local focus is covenant, worship, and faithfulness.
A plain takeaway is to answer the verse's own emphasis on "loving" and "jehovah" with trust shaped by these words, not by a vague optimism outside the passage.