I'd been living (and driving) in France for a month before my elder daughter was born. After the birth (and a long labour) I left the hospital at just before 6.00am - there wasn't another car on the road and I automatically headed off driving on the left instead of the right. It was only when I got to a roundabout 4-500yds up the road that I realised my mistake. When there are other cars about it's easy to go with the flow, it's when the roads are empty that you have to think twice.
in saying that, I opened the passenger door for myself nearly every morning during my first couple of years here, only to see that the steering whell was at the other side.
I also almost had a head on collision with a guy a couple of weeks ago. There are loads of roadworks in the town where I work and I was driving along a long one way street which, for the duration of the work, has had it's sense of direction changed. The guy I nearly hit lives on the street and, coming out his drive, set off as he's been doing for the past 15 years that he's lived there. It's easily done.