All we have is this moment, nothing more. To extend ourselves beyond that is to live within an illusion. What do we know for sure? I know I have this moment, this singular, ongoing, ever present moment. At least until it passes away, that is I pass away. We can come to see certain perspective truths through looking into the realm of ideas and by objectified time (projecting ourselves forward and back in memory and fantasy).
It's worth saying that there are plenty of ways to create meaning for ourselves, but that's just it, it's self created, not a priori. Most meanings and values exist only within the confines of our mental realm not as a pre-given part of reality. All we really have is this moment. We are sent into this world not knowing who we are, or what we're meant to be, or how we came to be. The only thing we are given is our ongoing moment to moment awareness.