Death is not the end of existence as some perceive it to be. Whether you are in Christ or not you will never cease to exist. Your existence is for eternity. Death is merely a separation. Physical death is the separation of the body from the spirit (and soul). The spirit (and soul) will continue to exist for all eternity.
Where one’s spirit spends the rest of eternity is entirely the choice of the individual. Out of Christ, the individual will spend all of eternity separated from God, this is the second death (Revelations 21:8), where the spirit is separated from God. In Christ, an individual will spend the rest of eternity with God because Christ is the first fruit of resurrection (1 Corinthians 15:20). And in Christ, all shall be resurrected into a new life with God (1 Corinthians 15:22). Those who take part in this resurrection will never taste second death (Revelations 20:6).
So then when a person dies, there is a loss that we experience that cannot be expressed in words. That is why we rightfully mourn. But if we know that the person who died was in Christ, then the mourning is but temporary and the joy of knowing that he/she will be resurrected and not taste second death, far supersedes the loss. Yet there are those with this knowledge who will not let go of their loved ones not just mentally but physically too. They periodically visit the graves where their physical body which once existed but has now decayed and turned to dust. Look at what Abraham did, when his wife Sarah died. He purchased a land far off from his sight and buried her in a cave so that her dead body would be out of his sight and he would no longer remind himself of the loss. Yes, he did mourn for Sarah but there was an end to it and life must move on and we cannot be stuck forever in a mournful state. That’s not God’s purpose for you, he wants to use you further and has greater plans in store that will take your mind off the loss you’ve experienced and bring peace and comfort into your life.