It's too easy to spend time in the future worrying about what's just around the corner. But "spending time" is a misnomer: we cannot spend what we don't have.
Maybe one day we'll figure out how to time travel. When that happens, will we be in a memory or a moment?
In our minds, we time-travel quite a lot. The irony is, it wastes time. I've heard and read that time is an illusion, something in our minds. Not being in the present is like a treadmill that never stops. Maybe it's better to just try and be present in the moment.