God made man as a person, and therefore made him with mind, will, and emotion. Each part of our personhood is part of our humanness. The emotional part of man allows us to express the various aspects of our affections, including joy and sorrow. We joy and sorrow regarding what we love.
The Apostle Paul wrote that when a saved loved one dies, we sorrow, but not as those with no hope (I Thess. 4:13). Sorrow is a natural emotion over loss. For believers, when we mourn the loss of a saved loved one, we sorrow; but coupled with sorrow is hope: confident expectation of a greater future. Resurrection is what we look forward to. Hope brings joy.
Joy comes from knowing that the saved loved one is with the Lord and that we will see that person again. The Lord provides joy as a blessing of being in Christ. Consequently, saved people uniquely have the ability to sorrow and rejoice when a saved loved one dies. The unsaved sorrow, but they have no hope and thus no true joy when a loved one dies. How sad!
Grieving is a natural part of death. It says that we love. But thank the Lord for salvation and for future resurrection. The time of parting is short, and some day we will be with the Lord and see our saved loved ones again.