Thoughts on mourning and comfort.

In my church we spend a great deal of time studying the scriptures. Along with the Bible, we have other scriptures that we believe contain the experiences and teachings of prophets who were called of God. One of our scriptures is called, The Book of Mormon, which is a record of God's people on the American continent.
One of the prophets from the Book of Mormon is named, Alma. He taught his people who were desirous to join God's true church that the requirements included being "willing to mourn with those that mourn; yea, and comfort those that stand in need of comfort." I've thought at length what that really means and have come to the conclusion that I have no clue.
A good friend of mine is now facing the loss of a loved one. To make matters more difficult, he lost someone who has always been a hero of his. How do I, as his friend, appropriately mourn and comfort him?
We believe that there is a glorious life after death, and that all will have the opportunity of hearing the true gospel and being resurrected like Jesus Christ was. We also believe that through a life a service, sacrifice, and obedience, family relationships can be preserved for all eternity. This knowledge is comforting to anyone who has ever lost someone special to them, and I know that my friend believes in this sweet promise from God. But the hard part is dealing with death from now until then. After the loss of someone very important to me, I knew that he was in Heaven, I knew that he was happy, and I knew that I would be with him again. My problem was the thought of life, this life, without him in it. Perhaps, that's where pain comes from in death; not from wondering if that person is alright, but from wondering if we're going to be alright without them.

To my friend who may or may not stand in need of more comfort, my heart aches that you have to be without him for a time. All I can offer you is my personal conviction and testimony of the words of inspired prophets. I know the Savior suffered, died, and was resurrected. Because of that sacrifice, peace can be found right now and families can be together forever. I love and pray for you.