Scripture tells us that all of us will have joy in heaven, but some people will have more joy in heaven (through rewards, crowns, treasures which they have earned while on earth). But if heaven is wonderful and awesome for everyone, how could it be better for some than others? Wouldn't jealousy and envy ruin it for some people?
Alcorn suggests that people will be like two sizes of jars - big and small. Both jars will be full of joy, but the bigger jar has a greater capacity. So if we act on earth in such a manner as to earn treasures in heaven, we will have a greater capacity to experience all the joy and wonder which heaven will offer.
This post was inspired by the book In Light of Eternity by Randy Alcorn.