Ultimately, everything is driven by ego. Even your belief that "a day will come when no matter what we do there will be no one to remember us or anything we did" is egotistical, as it assumes that you have some sort of special knowledge over what reality is all about. This almost nihilistic belief that eventually your life and what you did in it will be irrelevant assumes that you know more than you can. How do you know that this life isn't some "The Truman Show" level simulation and you're the star? Assuming that you don't matter is as egotistical, in a differnet way, as assuming that you have some divine, special purpose in this life. We really don't know either way. Maintaining a heathy degree of bewilderment seems to be the least egotistical option here, no?