Out of the billions of people that ever existed only a handful of them are still remembered today. If we think of Julius Caesar, Michelangelo, Albert Einstein ... all of those individuals left a mark that will likely be remembered for thousands of more years but there might come a point when history will forget about them too as in order to remember anything we need the ability to carry forward the knowledge from one generation to the next. In the event of a global catastrophe, that would prevent a generation to share its knowledge to the next, this chain would be broken only for history to start anew.
This is "okay" because it simply can't be helped. There's nothing, anyone, can do that will leave a permanent trace into this vanishing thing that we call time. A million years from now, humans may not even be around anymore.
Sometimes one has to wonder what's the point of all of this? A religious person might say that our existence is some sort of test that will determine where we'll be in our next, eternal, life. I always found it a bit strange that what ever behavior we have in our brief existence on this planet is, somehow, playing such a major role in another, more permanent, state of existence.
If we, somehow, lost all of our history and started anew it would be interesting to see what kind of religion humans would create for itself. My guess is that the Sun would, once again, reach deity status in much similar ways as our ancestors have... up until a prophet comes along to shake things up.