The way I think of it: I have experienced non-existence for billions of years, I will experience it again after my death.

Many people, religious or atheist, believe that the scope of life is finite in one direction: it starts at birth. Death is essentially the same thing, backwards.

Now, there are some people who believe their existence is eternal in both directions. For example, Buddhists believe in reincarnation, and I think the question of the first incarnation and even the very notion of a "beginning" is left open.