I cut my front lawn in long strips, one to the immediate left of the other. If you cut yours left to right, I have no issue with that. Agree to disagree.
Anyway, I say that because I have noticed a distinct tendency for my rows to drift to the left just as I am preparing to make the turn and head back in the opposite direction. The amateur psychologist in me thinks it is a tendency to rush through things, that I am eager to start the next stage — and therefore move closer to the finish line — before I have actually finished the current project.