First, live in England for three years when you're in your early twenties. Then practice driving on the left periodically on vacations to England, Ireland and South Africa.
Next, spend a month trying to learn how to cross the road on foot for drivers who will run you down before they will stop for you. Look right, left, right.
Then rent a car in South Africa. The first three times you go to get in the car, walk to the passenger side. Pretend you meant to do that and put your purse on the passenger seat.
Try to find reverse in a manual transmission car with your left hand on the gear shift lever. (I would like to point out that I do not care about any rental car's clutch or how how it sounds when I start from a dead stop in second gear.)
Next, once seated behind the wheel, reach over your left shoulder to not find the seatbelt. Adjust the mirrors, though this is nearly pointless because you will spend the next 50 miles looking out the side window to attempt to see in the rear view mirror.
When you do think to look into the center of the car and rediscover the rearview mirror, you will notice a black BMW directly on your bumper, because you are in the fast lane, as in the right lane and are driving far too slowly for his taste.
Get in the left lane after you turn the windshield wipers on for the 50th time, while attempting to find the turn signal.
Negotiate some of the worst traffic in the world without GPS because Verizon sucks, drive to the 12th floor of a poorly-designed parking structure, and figure out a multi-laned roundabout with trams and buses at 4:30 in the afternoon and you're well on your way to feeling comfortable on the left side of the road!
The roads are actually very good here in Cape Town and well-marked so I can't complain. Parking is free down at the beach and the car is costing me about $25/day. That's a deal compared to the Ubers, taxis and tours I would otherwise be taking.