Some have tried to answer the problem by holding that we would forget those people who are lost. The website Got Questions.org quotes Isaiah 65:17 which reads, "For behold, I create new heavens and a new earth, and the former things shall not be remembered" then concludes that "There is no reason why we could not possess many memories from our earthly lives. The memories that will be cleansed are the ones that involve sin, pain, and sadness."1 This view seems to say that anything that may cause us any type of regret or despondence will be wiped from our minds. But, that strikes me as odd. If God is so careful to give us free will and not to impose His will upon us then why would He erase significant portions of our lives from our memories? Would God really erase the memory of a particularly traumatic event, even though it may have helped shape us to be God-fearing?
John Piper, in looking at the same verse, doesn't take quite that stark a view. He writes, "What we will forget and what we will remember is not a simple class of bad and good. Rather we will forget and remember things in accord with what will maximize our enjoyment of God. If remembering something enhances our worship, we will remember it. If it would hinder our worship we will forget it."2 Piper notes the difficulty one has with the cross itself. Certainly, the cross is the most glorious thing since it reconciles us with God, yet it is also the worst atrocity in history as the sinless Son of God was tortured and killed by sinful men.
God is the one Doing the ForgettingI don't agree with either answer above. As I study the scriptures, I don't believe God will tamper with our memories at all. The concept of "forgetting" in the Bible doesn't mean unable to recall, but simply that the events are too insignificant to pay attention to. We see this in Hebrews 10:17 where the Holy Spirit states "I will remember their sins and their lawless deeds no more." God obviously cannot be omniscient and forget anything. So the phrase about remembering no more means that he will never bring it up again as the penalty has been paid in full. Likewise, the verse prior to Isaiah 65:17 uses the same idiom when Isaiah writes, "Because the former troubles are forgotten and are hidden from my eyes." Note who is doing the forgetting here – it isn't the people of the new heavens and the new earth, it's God Himself! God is doing the talking; therefore the personal pronoun "my" is referring to the speaker. Then, in the very next verse, God reinforces the idea by saying "the former things shall not be remembered." So, Isaiah 65:17 really doesn't speak about wiping out any part of the believer's memories at all.
In the New Heavens, We Will See ClearlySo, how can we have our memories of our painful struggles while on earth and yet be promised no more pain in heaven? I believe this is where the ability to see God's plan clearly becomes key. Paul tells us that "For now we see in a mirror dimly, but then face to face. Now I know in part; then I shall know fully, even as I have been fully known" (1 Cor 13:12). In other words, we will have a much fuller understanding of God's plan once we're in heaven. If God causes all things to work together for the good, as Romans 8:28 says, then God has made sure that any pain or sorrow we experienced was ultimately in His plan for our benefit. Paul also tells us that "the sufferings of this present time are not worth comparing with the glory that is to be revealed to us" (Rom. 8:18). Once we are in heaven, the trials and tribulations we place so much emphasis on will seem to us as a bad dream did one day later. Dreams feel so real when we're dreaming, but once we wake up, we realize how silly and ethereal they really are.
In another example, John writes of the martyrs who are in heaven in Revelation 6:9-10. He records, "I saw under the altar the souls of those who had been slain for the word of God and for the witness they had borne. They cried out with a loud voice, ‘O Sovereign Lord, holy and true, how long before you will judge and avenge our blood on those who dwell on the earth?'" It sure seems like the martyrs remember what happened to them! But note what they are asking. They are not calling to wipe away the memories of their martyrdom; they seek God's justice. They see the inherent sin of humanity (for the actual people who had martyred them are likewise dead by now) and they cry out for God to restore righteousness and out His creation back in order.
That is the key, I believe, to how one can be filled with joy in heaven even if ones friends or family are condemned to the judgment of hell. I think once glorified, we will see sin for what it is. Just as I answered in my article "How Can We Be Free in Heaven and Not Sin?", sin will appear so repugnant to us, that we will cry out for God to punish it. Our relationship will change because our understanding will change. We will see the righteousness of God in judging sin and we will recognize it as the holy act it is.
The idea of God wiping out any bad memories really doesn't make sense. After all, the Bible records all kinds of evil acts; does that mean God's Word won't be with us in the new heavens and the new earth? We know that Jesus will carry the marks of crucifixion with Him forever (Rev. 5:6) as well. Instead, it makes much more sense that our understanding of holiness will increase and our tolerance for sin will decrease to such a degree that we would simply see things a lot more like the way God sees them now. I know I cannot love anyone more than he does and knowing that any punishment is in the hand of a holy and righteous God, I can take joy in that.
2 Piper, John. "What Will We Remember in Heaven?" DesiringGod.com. Web. http://www.desiringgod.org/blog/posts/what-will-we-remember-in-heaven 20 Feb 2007. Accessed 25 Aug 2014.