I normally don't go for sports analogies, but you batted that one out of the park.

So even though we're aware that the entire universe exists, in terms purely of space, we for the most part perceive ourselves as existing only within the confines of our current surroundings--which represent, of course, only the tiniest part of the whole. I can certainly imagine myself anywhere else in the universe, but it's abstract and unreal. In the end, I am where I am.

The same with time: our surrounding "area" is the present--past and future are beyond our temporal horizon. Our senses are capable of perceiving--and perhaps our brain capable of interpreting--only our tiny local snippet of spacetime.

OK, so that might help explain the notion of "the present." What then differentiates the past from the future? For example, why can we remember the past, but not the future?