I am an atheist and also do not have an expectation of an afterlife, etc. I pretty much live like today could be the last day so I try not to have too many loose ends (e.g. important things not done or unsaid). Probably the most important thing I would do is make sure my girlfriend is ok when I am gone. But I don't imagine my world-view changing with that knowledge.
There are a couple of quotes by Marcus Aurelius I try to keep in mind...
“Do not act as if you were going to live ten thousand years. Death hangs over you. While you live, while it is in your power, be good.”
"Live a good life. If there are gods and they are just, then they will not care how devout you have been, but will welcome you based on the virtues you have lived by. If there are gods, but unjust, then you should not want to worship them. If there are no gods, then you will be gone, but will have lived a noble life that will live on in the memories of your loved ones."