To be clear, I personally do not believe in predestination. I find it to be a patchwork theology based on a rather silly notion.
But if God has truly "picked" those who He will save and will not save then the following may be of some hope:
2nd Chronicles 30: 17-20
Isaiah 38:1-8
Genesis 18:16-33
Maybe God will change His mind if the non-chosen will beseech Him in sincere prayer?
Maybe?