In today's Gospel reading from Luke 21 at morning Mass, while some people were speaking about how the temple was adorned with costly stones and votive offerings, Jesus said, "All that you see here ~ the days will come when there will not left a stone upon another stone that will not be thrown down." Indeed, nothing on earth lasts forever. Even the galaxies are not stable as old stars disappear and new ones are born constantly. Moreover, our earth has only limited inhabitable space and thereby cannot accommodate an unlimited number of inhabitants ~ it should be clear that God did not mean the earth to be our permanent residence.
Since everything passes, our life can only be made meaningful by including God who is everlasting. Even if I perform the most memorable deeds so that the whole world will know me and praise me, one day I'll be totally forgotten. We admire and look up to a lot of heroes of the past, the souls of some of whom might not even be in heaven ~ this is even worse! The point is that if we live for the glory of God alone, then our lives will become meaningful, and my souls will get to live forever with the one who is everlasting as well.