the music is going up or down, high or low, the music will always flow from left to right (ie like reading a book).
but (and this is where it can be challenging!) your hand movement on the piano itself will sometimes go from right to left (ie if the sound is going down) while your hands will move from left to right if the sound is going up.
so, taking the music extract below as an example, in the first bar the actual piano keyboard keys (and therefore your fingers/hands) would be moving from left to right (going up); while in the second bar, the piano keyboard keys (and fingers/hands) would 