Temporal Gravity

So in one of my reflective moments today I was thinking about space, geometry and planes. How do you create movement if you're in a space (with little to no gravity) with no friction and nothing to move against? On Earth we can move easily in two dimensions most of the time because we have something to move against (the ground) and gravity is not pushing against us in that direction with a striong force. Try moving "up" and it becomes more difficult, since we are trying to move directly against gravity and we have nothing to move against. Dive into a pool and suddenly you can more easily exert force against gravity and move up through the water.

So what about time? Why is time such a special dimension that we can only move in one direction? Is it that we just don't understand the opposing force that keeps us from moving backward? Like gravity that keeps us on the ground, is there a temporal gravitational force that keeps pushing us from behind as we move along the 4th dimension. How do we go about descibing this force, and how do we defeat it?