I spend a lot of time thinking about what makes people human. What separates us from animals, even ones that make tools and perform complex tasks?
"Wow," you're thinking. "She must be really cool if she spends her time thinking about deep questions like that."
Your assumption is understandable, but debatable. To be fair, though, I have to admit that I think about this question so much because it is one of the foundational issues I've been led to explore in my program of study: Communication. The Comm. program at my school is based on rhetorical theory and argues that people's ability to communicate (use and create language) the way we do is the thing (or at least one of them) that sets our species apart.
The writer of Ecclesiastes says, "[God] has also set eternity in [humanity's] heart" (Eccl. 3:11 NASB). To me, this says that humans have a God-given ability to think beyond their present circumstances - to communicate, both internally and externally, about things instead of only being able to experience them.
In some ways, this ability to think, and therefore live, outside of our personal realities has limited our ability to function - we are almost always abstracted to some degree from pure existence. But in other ways God opened up the entire world to us by placing us both within it and outside of it - by giving us eternity.
This eternity enabled not only communication, but also hope, and faith, and trust, and goal-making, and relationships, and on, and on. And these things are all inextricably intertwined because they are all threads of the eternity in our hearts.