A practicing stoic must often reflect on their mortality. Momento Mori, a common stoic theme, is to remember that someday we will leave this life.
Our eventual passing can be scary to think about. Trying to fathom the infinitude of nothingness can be overwhelming. When I went under for both my shoulder and quad surgery, I was able to get a glimpse of what it is like to go outside of time and into nothingness.
The fear disappears along with time. The passage of time is meaningless, as is the fear that you may once have had of this particular moment. The practicing stoic should meditate on this and let that fear pass.
I have no fear of ceasing to exist; it is the same as not having begun.Seneca in Letters from a Stoic