Democritus' statement as worded is easy to understand as nihilistic - as saying that nothing exists unless we agree it exists other than atoms and void.
For me, it doesn't read that way. I've always taken it as a bare statement of fact. To try and imbue existence - let's get personal, your existence or mine - with some transcendent or ultimate meaning is, by definition, a meaningless endeavor. We're ALL, at the core, temporary patterns of atoms in the void. But not JUST atoms and void. We do have a real life and interact with real things in a real cosmos at the macro level of everyday existence. We don't experience ourselves as atoms and void, but we should keep that thought at the back of our minds, especially when we hear "God has a plan for me" or "The Universe is showing me a path." We give our lives meaning, and we can experience a pleasurable existence. But that doesn't mean we aren't, at our foundation, atoms moving in the void (or whatever modern paraphrase one wants to use).