“And there you will remember.” When the Israelites are back in the land of Israel, which will occur at the Resurrection of the Righteous (the First Resurrection), the people will remember how they lived their first life, and if they were sinful and selfish, they will hate that they lived that way.
“and you will loathe yourselves.” This is very strong wording considering that it is speaking about people who are saved and alive in the Millennial Kingdom. Many people who are saved and have everlasting life never make the effort to live a truly godly life on earth. In the future kingdom of Christ there will be a distinct difference between those people who made the effort to live truly godly lives and those people who got saved but continued living selfishly and in sin. The people who have little or no rewards in the Millennial Kingdom will realize why that is, and will be ashamed of their selfish lives.
[For more on shame in the future life, see commentary on 1 John 2:28 and 2 Cor. 5:10, “good or worthless.” For more on the future Millennial Kingdom, see Appendix 3, “Christ’s Future Kingdom on Earth”].