I'm very sorry to hear about the loss of your friend. I have a different take, which might also bring you comfort (warning, it may do the opposite).

Many people speak about a person "being" with a singular "stop being" we call "death" or "the passing of a person". I understand why we do this, because from all outward appearances that's what it looks like. However, its not actual, in fact so. In fact, almost our entire body at the time of our death has nothing of our original body. Skin is replaced in weeks, while at the other end our skeleton has about a 7-10 year cycle time. From what I can gather, besides a few hundred grams of cells in a few places in our body, everything else is replace many times over the course of our lives. We are, all of us each, a walking "Ship of Theseus".

So by middle age, our entire bodies (again besides the few hundred grams) have been changed out multiple times. The fingers you're feeling with, those aren't your originals. The certain structures in the ears you're hearing with have been swapped at a cellular level from what you were born with. The living cells in bones of the legs you stand on have been grown, shrunk, ,and replaced cell by cell until nothing living in those bones is your 'original equipment'.

Further, you've experienced life and your views have changed since your youth. You've been exposed to different environments and chemicals which will have subtle effects on your cognition. When compared to your youth, you are neither the same person in mind or body.

What we draw from this is that we have "mostly died multiple times already". How does it feel? Do you mourn for your former self(selves)? Is the world missing the former "you" or did your actions when that person existed still echo in the world? Did your good works and helping hand still live in the memories of those you assisted?

If so, then when your final copy of your body is on the edge of being retired, your actions and the spirit (as defined as the actions you produced over your life) are noted and know to those you touched. Will it be so different from the multiple times you've "died" already?

All of our atoms in our bodies are borrowed. We'll simply be returning them from where we got them. Where do we go when we die? The same place we were before we were born, pieces of the universe in use with other objects and beings.