Why does death make life meaningful?

Why should she who was of a gentle and unselfish nature have to undergo such long drawn-out suffering? She would not let go physical life until death had beaten her into a corner.

There are many gentle, beautiful souls who have been brought up with the idea that death is terrible and that we must hold on to the physical body until the last possible moment. Such souls do bring to themselves much unnecessary suffering, especially if the creed of punishment has been imbued into them. And because they think this earth is the only place where they can really atone, they cling to it and pass through much suffering before they let go. 

Another reason is, of course, karmic. 

Such persons must incarnate again upon earth and they incarnate with all the beauties of their devotion, all the lessons they have gathered, all the desires for a higher and better life, but they have not as yet learned the true lessons of life. They often pass through the karmic result, not only of their sins, as do others who have been more worldly, but the results of their beliefs. 

The higher plane is for those who are ready to receive it—all that you can contemplate of heaven and joy. 

Letters from the Teacher, Volume II