West to east seems harder.
On an overnight flight from O'hare to Heathrow, I thought for sure that I'd be feeling pretty good by the time I arrived since I normally stay up through the night anyway.
Maybe it's the disorientation of being on the plane or just the excitment of the trip or some combination of many things that mixed me up but by the time I got to London, people were having a hard time understanding me....and I speak English.
The trip back was better....I had written questions and replies on index cards
West to east is harder without index cards.