That which is temporary is, well, everything. This is a disturbing thought to the ego so it rarely goes there, and when it does, it recoils away from thinking about it because in thinking about it it realizes (though it tries to forget) that it too is temporary and the ego cannot 'live' with that.
To be temporary means that peril to one's existence is always there. Existence can be diminished or it can cease altogether. What comes after ceasing to exist is either a very good place, a very bad place, or no place and no sensation. That is about it. Fantastically good, unimaginably bad, or nothing.
Temporariness means that the passage of time is marked as well. There is a beginning and an end. Start of story, end of story.
Recently, a famous scientist passed from this world and awareness on the man and his works was heightened but soon he will fade from the scene, as all do, for his works will be dated with the stamp of time. When you are here what you do is current, when you are not, you might still be important, what you said or did might still have weight, but measured against curent events it will be and if you were still here you might be saying something different now, right? So, you're valid as long as you are alive. After that, you are invalidated, in a way, due to simply not being physically present because the data set changes. New things are always being introduced.