Inasmuch as Ye Shall Keep My Commandments Ye Shall Prosper in the Land

Lehi testifies to his sons that God is eternally consistent and how they will fare (physically and spiritually) depends on their choices in relation to God’s standards:

His ways are righteous forever. And he has said that: Inasmuch as ye shall keep my commandments ye shall prosper in the land; but inasmuch as ye will not keep my commandments ye shall be cut off from my presence.” (2 Nephi 1:20)

Questions:

-What does it mean to prosper in the land? And, how is it the opposite of being cut off from God?