Why are people, as a rule, saddened by the death of a loved one?

I'm a 22 year old Christian and i've had the fear of my parents dying ever since i was around 8 years old. just because we're christians doesn't mean its easier said then done. Yea its ALOT more comforting to KNOW that we will see them again, but the worst thing about it is that we have to WAIT a long time to see them, depending on how long we live. Take my parents for example, i KNOW they are going to leave me one day, and i FEAR that day. I will miss the laughter of my mom, i will miss waking up in the morning hearing her knock on my door to get ready for the day, i will miss going shopping at Wal-Mart like we ALWAYS do, i will miss talking to her or watching or waiting for her to come home after work. As for my dad, i'm going to miss just walking in the room and seeing him doing work on his computer, i'm going to miss him dropping off at school, i'm going to miss teasing him. i mean its that fact that its a loved one that you're not going to be able to see, hear, or touch ever again until its time. its VERY ROUGH. i wish i was like you, because i'm going to cry my heart out when the day comes. i may even be depressed for a long time. but we grieve differently from others. so thats my answer.