You can never be destroyed or annihilated. Your existence is secured for infinity. You might forget about this fact from time to time, and hence the reminder.
What are you basing this on? What makes you say our existence is secured for infinity? I live my life day to day because of how limited i know my existence is and at the end of the road, it won't really matter if i live or die, or if i do something or don't so i find it pretty interesting that when talking about such a traumatic situation you say this.
And how do you know that your existence is limited?
I've been close to death twice in my life, i felt how my own life was ending and i had no memories flashing on my head instead i had regret because once i felt like that once too, i felt like i would go on forever and i too thought i would go on forever, like the universe would vanish and i would still be here... but when you realize your life can be taken away in a snap by someone else... when someone puts a gun to your face and is ready to pull the trigger if you don't do what they ask, you come to the realization on how limited and powerless you are.
Those events made me change my outlook in life and in fact, accepting that my existence is limited and short has helped me a lot in taking life way easier, because it doesn't really matter what you do... memento mori.