How useful is it for an organism like us to ponder our ultimate doom? It is scary because if you take the common rational assumption of death then you will unexist forever.
In my experience, when I perceive this concept (that I will be lost forever) deep down with lots and lots of clarity (I mean not just thinking about it but really understanding what that means), I usually find that I get anxious for a few moments and then suddenly I feel like I just want to get it over with as fast as possible as delaying it any further is just pointless. So in other words, a supposed delusion exists that sustains my desire for life and once that delusion is broken with clarity in to the nature of the concept I will not exist forever then death becomes desirable as there is no other alternative. The same thing, I assume, occurs on a smaller scale when you bring up the concept of death will people in conversation, it suddenly sparks some depressive emotions and these depressive emotions are equivalent to the result of desiring death on smaller scale as the realization in the participant has not become fully expressed in his/her mind yet due to conversation being localized in language rather than deep introspective and existential analysis and therefore manifests itself as both depression, confusion and a desire to change the subject to more light and convivial things like how to make strawberry cupcakes
Now this is the issue with our western societies' common sense view of death; knowing that you become n0thing is anxiety provoking until the point people feel they just want to get it over with. IE, companies like DIGNITAS for people who have a terminal illness.
Of course this is only one scenario of thinking about death, there are many others. The question here though is how does this benefit us? Surely by thinking of the end of what we are enables us to define the value of what we are. We do not need to live forever to give life meaning so why then under the
pure and direct realization that we are going to die (not just thinking about it) do people perceive that their life is worthless because they will be annihilated for all eternity? More to the point how does thinking of death benefit us? Does it enable us to see the value of our lives more clearly?
IME, DMT has always made me ponder death a lot, among many other things also.