10 years after my death things will still matter. I'll still have helped my parents when they were old, I still will have loved all the people I loved, I still will have enriched the lives of those around me, I still will have brought joy, and so on. If these things don't matter, then why does the 10 year figure mean anything? If those things don't matter then they don't matter now. But they do matter now. Clearly they do.

EDIT to anticipate replies:

I think in the atheist community on reddit and elsewhere there is a fundamentally theistic move going on, which is that things can only matter if there is someone to which they actively matter. We posit god because in order for us to matter after we die, we need to posit a being with infinite cognitive power that exists indefinitely. But we don't. Things can matter regardless of anyone finding them important. Mattering is in the matter so to speak.

Just consult your intuitions. Think about something simple even, like doing a homework project. Sometimes the crucial piece of information is in a place you didn't think to look. That piece mattered, and it mattered before you looked there. It just did, regardless of whether you ever found it.