Ok this going to be very difficult to explain but I will try and break it down into sections so you can understand where I coming from, though I'm not sure if I understand this myself. I may have just got the wrong end of the stick in relation to something that is very simple to understand so bear with me.
1) The universe (our universe as we know it to exist) didn't always exist so it had a beginning with the big bang.
With the big bang time as we know it began, time moves forward in this direction, past ----> future
2) After 13.75 billion years the first known (though very likely not literally the first) fully self aware life evolves in the universe, this being mankind. Many other animals will also be aware to some degree as well of course though not to our level as they have much smaller brains. So conscious awareness is firmly linked to the physical brain.
3) Any one individual fully sentient being has a finite existence within the time flow of the universe in that there was a time that existed before they existed, the universe as we know it is finite in much the same way though time only came into existence with the universe itself. However they only joined with the flow of time once their brain was developed enough to enable general awareness, at first this awareness will have equivalent to that of a tadpole, but this still counts. This awareness develops into greater complexity through development in the womb, after birth and from infancy into full sized brain adulthood. With this greater awareness we can experience the flow of time, remember the past, experience the present and plan for the future.
4) There must have some exact instant of time when an individual sentient mind will come into existence from non-existence. The mind itself was created from something else that had physically existed before. For instance all life on Earth could in theory be traced back to one living cell, that living living cell was created by some naturally occuring physical process and so on until you go back to the naturally occurring original cause of everything that exists. But we're getting off topic here.
5) The sentient mind though a product of the physical body is also a product of something which is not in itself physical, this being the flow of time as without the flow of time no conscious brain activity or thought can take place.
6) So we have a situation here where we are flowing forward through time from a point in the past to a point in the future, though from our point of view it will always be the present regardless of the time we find ourselves to be within. For instance here is my past (and present) self *waves* and now I'm flowing forward in time (while staying in the present) along with the rest of the universe *whoosh* ----------> and here I am in the future (present) as my future (present) self *waves*. So what I have done here is flowed forward from my past self into my future self and this was a forward motion I could in some way consciously perceive taking place despite the fact that it was always seemed like the present. If I could not experience this forward flow of time my consicious mind could not exist, at least not in any coherent form that would make any sense to us.
7) So far so good, but assuming the sentient mind is entirely dependent on both the physical brain and time in order to exist (and there is no such thing as a soul ) we hit a slight snag in the process. The problem is we can't of course travel forwards forever as there will come a point when all physical functions cease through the process of dying and becoming dead. On death not only will your sentient mind cease to exist you will also stop travelling forward through time and experiencing the future time as the present.
8) Ok so getting to the main meat of the problem here, run the example of myself flowing forward in time as before but assume my future self instead of being alive in the future is in fact dead, and this will of course happen at some point in future, so watch this.
Past (present) self *waves* and now I'm going to move forward in time with the rest of the universe (while staying in the present) like this *whoosh* ----------] *BANG!* as you can see I've hit a brick wall as there is no future (present) self for me to flow into, which you could confirm by proding my unmoving stone cold body with a stick at this point in your present which is my post death future and non-present. However I would still be experiencing everything up to the moment I snuffed it as the present time while moving constantly forward into the future non-stop. But if you look my past self is still back there in what my past self thinks is the present but my past self hasn't and would not be able to move forwards into my future post death time period. The post death period for me is the present living time for you and everyone else who aren't dead yet and the people who will be born at some point in the future after I and everyone else in the world alive right now will be also dead.
9) So can you see the problem with this? Or am I seeing a problem where there really is no problem at all?