Pls. show the pot & mix it was in (as it appears to be rotting from the inside out). That looks like old peat around the roots, I'd remove it ALL.

It's not just how much one waters, also the type of mix used (how water retentive it is).

It was actually in my wedding bouquet! When I threw the bouquet out I noticed the succulent had some roots, so I stuck it in some normal potting compost because that was all I had and I thought it was worth a try. It's hung on for a few months and appeared to have grown roots but has suddenly started losing its leaves. Help!

even if you only water it once a month, if your container/pot has no holes and you water it deeply w/o waiting for the water-retentive soil (your normal potting compost) to dry completely, you can create dangerous conditions for your succulent.

Your humidty levels, temp, pot size, pot material, and amount of sunlight the plant is exposed to, can also have an effect on how your succulent grows.
Let us know the environment it's in. the forum will be able to better assist you.
but as imontestella says, it sounds like rot...
If it is rot, you may be able to save it. can you post a picture of your succulent from the top? or an angle where we can see the whole plant?

perhaps, what you can do in the mean time, is gently dust off as much of that soil from the roots, pat the roots very gently with paper towel to remove any excess water, then leave it on the paper towel in a dry area....

One needn't be so gentle, these are tough plants, used to dropping leaves & restarting where they fall. No one to right them or gentle them into existence. Just crumble the soil off w/ your fingers, these aren't plants needing such TLC.

Just whatever you do, pls. DON'T WATER IT/THEM for at least a week.

heh. i baby my plants too much. :)

Sorry, no, I must respectfully disagree; for a newbie it's bad advice.

PLS. DON'T CUT anything as I'm not sure you'd know where to cut & you're likely to cut off the bottom of the crown inadvertently (which will kill the plant for sure).

Having removed as much soil as possible, I can see the stem is eroded at soil level and it's a bit squashy and brown. The top seems fairly healthy. Is there anything I can do to save this plant?

The stem is squashy. Will it not just continue to rot? I don't want to cut it but just thinking if cutting is going to be my last resort, perhaps it's best to attempt it before the rot spreads any further?

Soft stem is most likely rotting. Depending on how far the rot spread, it may or may not be possible to save it since there is no stem to cut the rosette off and root it. Looking at the photo, rosette doesn't look that great: leaves are quite light in the center - BUT that could be just light color from insufficient light or maybe lighting when photo taken. Only you can tell. Are the leaves also soft?

If there is rot in the stem, it will kill rest of the plant. You may not have other choice but cut the roots off and see the stem - if there is any discoloration (should be light greenish or creamy color without any dark markings), the rot has set in. You could try cutting off another thin slice - depends on how much stem there is. Take off few leaves and cut - post photo of the cut. And I would do it sooner rather than later, rot spreads fast.

You could take off some leaves by twisting them off gently, and try to root them to grow new plants. No guarantee - the leaves should be healthy. But probably worth trying. I would take off 4-5 lowest leaves, lay them on top of mix and just wait. No watering.

The middle is indeed very light and a bit floppy. I don't have any stem at all - as I said, it had been cut and was wired into a flower bouquet. I removed the wire and re-rooted it. It has hung on for several months but doesn't seem happy. Sorry if this has caused any animosity - I just wanted to know how to save it if possible.