What reminds us of the people that are no longer here? Photographs? Videoclips? Neuron action potentials and long-term depression in the brain?
What stays after we are gone?
Some might say that we stay in the memories and in the genes of our children. In the teachings we give them and in the moments we create together.
Other might say we stay in the memories of mankind in the great or awful deeds we accomplish during our lifetime.
I don't know what stays behind after we die. Of course I don't know... how could I. But I think. No... I believe that it doesn't really matter. When we are gone, we have other things to worry about than how/if the world around us remembers us? The world will keep turning, people will or won't grieve, will or won't remember, will eventually forget. And even if they don't, their children or grand-children will. That's the way it goes and that's not the point here.
Every being is different, which btw makes life much more fun, and each being leaves a distinct imprint on the world. There doesn't have to be something that reminds or someone who remembers. It's the same situation with the tree in the forest in the Zen koan. If the tree falls and noone is around, is there a sound? Is there a sound if there's noone to hear it?
The answer is as easy as it is universal: it doesn't matter. The tree is the main person here. Why should it matter, if someone hears it fall or not. It falls. We always want to make it about us, when it's the tree that's falling... stupid humans.
We are born, we grow up, we age, we die. And it doesn't really matter if someone is there to witness it, because in the moment all that matters is life. Life happening. Not some echo... Life.
So make the best of it :-) Even on Valentine's day. Don't worry about things that might or might not happen. Live a little ;-)