We associate the day mostly with sin and repentance, but it is in equal measure about death and how we understand and cope with it.
In its origins it seems to me these two themes were clearly connected because transgressing - לחטוא - (sinning - it does not mean quite the same thing in the English translation) was seen to be something that offended God and for which one could be punished - accumulating to a shortened life.
[Squaring the circle with the view that God foresees and knows everything and, moreover, is the cause of everything, is the irresolvable contradiction of all such world views.]
But, in the way it has evolved down the ages until today, with the myth of the supernatural less powerful, and the imperatives of community coming to the forefront, these two parts (repentance and death) seem less connected - but no less poignant We still have to deal with death. "Though I walk through the valley of the shadow of death, I shall fear no evil" - be comforted.
When hearing the names of the long list of congregants who have died this last year, I had these thoughts. Reminding ourselves of the inevitability of death is like teaching economics - one cannot avoid the (budget) constraints. But, there is comfort in the knowledge that though each of us is destined to die alone, we need never live alone, but may choose, until our dying second, to live connected to those we care about. Yom Kippur is about living connected lives.