Alex, depth perception is an individual thing. There are ways to tell how far away your plane or any other object is, and should be practiced without the plane speeding around. While someone else is flying, start looking for clues as to how far away the plane is from you, how far the plane is from the ground. After you get used to this you can judge it much quicker as you fly your plane.

Look for the plane's size in relation to how big it was on the ground. Look for shadows before you take off, the angle won't change much by the time you are ready to land so after a few low passes you can start to guestimate altitude.

I used to fly with a pilot that had one eye, how much depth perception do you think he had?

If you think about it, If you are having problems landing a plane that is within 400 feet from you (assuming you stand at the center of the runway), How do you expect to drive a car at 70MPH and come to a smooth stop at a red light behind another car?

You might think the car is irrelavent, but it's not. In fact that is also a good time to start looking at objects around you and judging how far it is from you, or if it is on an incline. If you have been driving for at least a couple of years, you probably do the calculations without thinking about it. Now it is time to relearn and adapt it to your flying.