I love succulents and have quite a few different mesembs that I'm managing to keep alive. I think of mesembs as goldilocks plants: You have to get everything just right, but they are relatively resilient and I have learned to pick my battles. Then we come to the ones that are like The princess and the pea. No matter what, they refuse to get comfortable. Not for beginners and sometimes, not even for experienced growers, unless you become the slave of your plants and even then... Most of these plants grow in extremely arid climates, some of them have evolved to the point where they get most of their moisture from the dew and are mostly just water storage containers that will rot at the drop of a hat
The Split Rocks and Stone Plants
Lithops can be deceiving because some species are relatively easy because they aren't all found in semi-desert areas - some even grow in grasslands. These can tolerate more watering than others although all of them will swell and swell until they burst if you leave them outside in the rain. I was getting relatively good at keeping lithops alive until I got a cat who thought that sinking his claws into them was just the best thing ever. Although that particular cat met a sad end on the road, I restrain myself from getting more.
I killed the first split rock I got by overwatering it and I have another but I have learned my lesson. It wasn't doing well, the roots weren't happy but I didn't water it and seems to have turned a corner. It's making a new set of leaves, anyway. Maybe it will reward me with a flower.
Image: Alan Rockefeller, Wikipedia
Plants like Dinteranthus: I'm not even going there. Google that: they look amazing but aren't easy to keep alive
Babytoes aka Fenestraria
Image: Stan Shebs, Wikipedia
This one rotted on me within 3 days of bringing it home. Apparently, that's not uncommon. I think next time, I will just get Frithia, aka. fairy elephant's feet, which come from grassland areas near to where I live, although they are relatively rare in the succulent trade.
Conophytums
Image: Wikipedia
These want full sun, but only for a few hours a day as they normally grow in cracks or between rocks, which keep their roots cool. They get their water from the dew as it seldom rains where they are found. Beyond goldilocks but maybe one day I'll try it, If I find the perfect spot. Fortunately, these are also relatively rare in the succulent trade so novice growers can find something else to disappoint themselves over