I had forgotten that, but now that you mention it, I had the same experience.
Haven’t been in Ireland, but in Great Britain I’d agree:
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back-country roads are much narrower and, in some cases, more poorly maintained than their U.S. counterparts.
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roundabout traffic moves more quickly there than on the few U.S. roundabouts I’ve been on (there are a few in the outer eastern suburbs of Cleveland, An Gadaí).
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more animals (sheep) are on the roads in rural areas.
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I found it frustrating that street signs tended to only name the next small town down that road, not the big city toward which you were ultimately heading, which meant you had to follow on the map much more carefully to be sure you were still heading in the right direction.
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never had a particular problem staying on the correct side of the road.
The first left turn was totally weird. I kept thinking, “Okay. This is just the opposite of a right turn in the US.” But it didn’t seem like it.
After four hours of driving around on the wrong side of the road, I signed into my B&B with my left hand! Normally I use my right for writing. But I’m fairly flexible about this.
For some reason the road maps looked very different to me, too.
Good luck finding an automatic.
I find it easier, rather than thinking about left/right, to think of it as “I (the driver’s side) should be towards the middle of the road”.
Roundabouts are easy. Forget about the roundabout; just imagine you’re at a t-junction and need to turn left. Then follow the road until you need to turn left again.
I was constantly putting on the wrong turn signal. It was like in my mind, I had decided that everything was opposite, so that if I intend to turn left, I should put on the right turn signal. Then, as soon as it was blinking, I would realize my mistake and switch to the left turn signal. I’m sure people driving behind me thought I was hopelessly lost, or just plain stupid.
And which lane are you going to be in on those roundabouts that have two or three lanes?
(I’m surprised we haven’t had a Magic Roundabout link yet.)
When in doubt at roundabout, keep going. Better to make an extra circuit than to hit something.
I guarantee that the first few times, after you park and then come back to the car, you will first open the passenger side door and get at least partially into the car. This will be a source of amusement to any Brits who may be watching.
Being English but have lived in America for 15 years, I am used to the transition. However, the thing I have most trouble with is hitting the door with my hand when going to change gear.
I still do this very occasionally in the US, usually when the car is parked on the left side of a one-way street.
This doesn’t really apply to your situation, I don’t think. But if both driver and passenger are new to Ireland and driving on the left, the passenger is the navigator and in charge much the like anesthesiologist in a surgical procedure. The driver does nothing but keep the car on the road safely and do whatever the navigator says!! 
With one exception. The driver must actively ignore gasps of terror from the passenger. It only *looks *like you’re going to hit that rock wall.
The biggest problem I had was landing in Dublin and getting the rental car. It was my first time driving on the left and when you leave the airport you’re thrust right into heavy city traffic. You’re kind of forced to adapt quickly!
The other thing that took some getting used to, was driving on the twisty, extremely narrow cliffside roads WITHOUT GUARD RAILS as a native was on your bumper beeping the horn at you because you’re driving slow enough NOT TO DIE by going off the one-car-width lane and into the sea below, which is apparently, too slow. 
Staying in the correct lane when turning, banging my hand against the door when trying to shift, mixing up the turn signals and windshield wipers, constantly getting into the wrong side (just act like you meant to do it).
The turning thing messed with my head when I came back to the states. It was like someone fiddled with my brain’s operating system.
I never had any problem with left-hand driving. The fear of a grisly, violent death pretty much cemented the habit within an hour or so.
I will however admit that now and then, when getting into the car, I would get out my keys and promptly seat myself on the passenger side. I never completely broke that habit because the only negative consequence thereof is a brief moment of “huh, some prankster moved the steering column. Oh wait, I’ve been living overseas for the past year, haven’t I?”
I couldn’t agree more. I have driven through the Welsh countryside twice, each time for over a week. As long as I recited my “drive on the left, look on the right” mantra, I was fine.
The more difficult part was not the reversed direction but the country lanes. These lanes are often single-file traffic with high walls or ditches on either side. It can be very difficult to manage oncoming traffic, especially when the locals drive at terrifying speeds.
In well over 1500 miles of driving in Wales, the worst I did was striking off the driver side mirror against a stone wall in a country lane.
My wife and I have visited Ireland twice from the US, and the driving was definitely an experience. We did not really have much problem adapting to the left lane thing, but the narrowness of the roads coupled with the fact that there is rarely a shoulder was really unnerving. These huge trucks (or lorries, if you prefer) would be barreling down the road and it just seemed certain they were going to plow right into you, and there was no way to “lean” to the left because there was a damn stone wall (or hedge or something). The speed limits on some of the roads seemed ludicrous, too. We actually took a photo of this ridiculous narrow country lane - just enough room for one car - with an 80kmh sign. :eek: Second time we were more prepared for it, and we had a smaller car, which helped.
Note that is was the Republic, not Northern Ireland.
ETA: And I should have read Maeglin’s post, which beat me to it 
So, um, ditto.
Tsk, should have phrased it, “When in doubt at a roundabout, don’t get out.”
Whats scary about round abouts. Go with the flow.
If in doubt, the left lane. Unless you’re going right.