Just a matter of getting used to it.
Jeep offers right hand drive for mail delivery. My mail deliverer uses hers as a daily. I see her often doing 60 or better when she's not stopping at every mailbox.
It's not so much the speed that may be the problem.
Picture yourself driving from the passenger side when you want to pull out to the left to pass a big rig on a two-lane road.
It's no longer an issue of pull out just a bit to see if traffic's coming. You'll have to have over half of your right-hand-drive car over in the opposing traffic lane before you'll be able to see what's about to run head-on into you.
I've got a Mopar buddy that lives in Oz and he's told me that this is a BIG problem when driving our left-hand-drive classic Mopars down under.