The point of reference is the pole(s). When the north pole is 90 degrees to the left of your path of travel, you are heading east; when it's 90 degrees to the right of your path of travel, you are heading west.

You can travel "infinitely" east or west in this was because all east/west "lines" are circles when looked at from a universal perspective.

Old Man Henderson moment

Boobs

Angels according to me

On a universal scale, yes. But the cardinal directions of a compass are not taken with respect to the universe, they are relative to points on a sphere.

It's kind of like this: if you walk towards the center of a room, you eventually reach the center and then can only walk away from the center, even if you continue walking in the same direction relative to the rest of the universe.

Alternatively, you can walk around the perimeter of a room always keeping a wall on your right side. No matter how far you walk, no matter how many times you circle the room, you'll always have a wall on your right side. Sure, you'll regularly change direction relative to the rest of the universe, but that isn't what you're basin movement on in this example.