4 [“] He will wipe away every tear from their eyes. Death will be no more; neither will there be mourning, nor crying, nor pain, any more. The first things have passed away.” - Revelation 21:4 (WEB)
If you what to do things right, you need to do them in the right order. You need to build the foundation of the house first, before you try to paint it. You need to learn to read before you can study to be a school teacher. First you learn to walk before running in your first marathon.
God's plan is the same way, we must take the “things” as they come. Before a new heaven and a new earth can come about, we must deal with the first “things.” Though God's creation was very good (read Genesis 1:31), Adam's sin upset God's plan, Adam did not follow what God had wanted him to do. Yet God did not give up on Adam or us, but had a plan for us in place, His Son Jesus Christ. Christ had to come first to do away with mourning, pain and death. This is the order of “things” and if we stay with God's plan (following Jesus) we will see the new and great “things” that God has in store for each of us.