...in the only world we yet know is only right.
We have loved and been loved here. To grieve the loss of that which is lost is to intrinsically understand, whatever faith we profess or do not profess, that deaths and ends were never meant to come to us in this once-perfect Eden.
The New International Version's translation of Ecclesiastes 3:11 contains this line: "...He has also set eternity in the human heart." We, the people we have loved and known, the people we have never met, and the creation in which we live were all made for eternity. But death and endings have invaded this place, invaded us, through human sin.
So, it's right for us to mourn and sorrow over what is lost, even those of us who are assured that by God's grace through faith in Christ, the One Who died and rose again, we will step beyond the portals of death, step into eternal sunshine, where loss never happens, where every greeting is hello and not goodbye. There, God will dry our tears and call us further in and further up into the eternity for which we were made.
I love C.S. Lewis' portrayal of grief and eternity in a scene from my favorite of his Narnia books.