repot it into a fast draining mix in a pot with a drainage hole. Remove all old mix when repotting, and cut off any rotted roots.

Put it in a different pot? Drill a hole in the bottom, although you would need a special bit. A small terra-cotta pot would do nicely, and you may still be able to use the one in the photo as a cachepot (stick terra-cotta inside it but take it out for watering & draining). Check soil. Yours is probably too peaty. You want about 50% pumice or perlite (or even more). Water thoroughly but only when the medium dries.

As Ariel said, a small terracotta pot is best or plastic can work too, but not too big. That style pot with the rounded sides holds too much moisture with the extra problem of no hole and water retaining soil. I would not wait to do this; your plant isn't looking good.

My opinion, I would not use that as a cache pot. There could be humidity or moisture between the planted pot and the cache pot which would not benefit your plant. I'm not a fan of cache pots for succulents.

In my opinion, Haworthias should not be misted, which you said you did. The advice you got above from the last three posters is exactly what I would suggest too: new and grittier soil, new terra cotta pot (smaller size), water only when dry, and give it bright but shaded light -- not direct light.

You might want to read up a bit on succulents before buying more. They ALL need the care suggested above, terra cotta or plastic pots w/ drainage holes (a must). Pls. don't mist succulents, it can lead to rot. These plants do not want direct sun, more bright shade, like off to the side of a window.