Updated: May 3, 2018
Have you noticed your succulent shedding leaves or drying out quick? For the most part, it is normal for the lower leaves to shed because new ones will form. However, if the leaves are yellow and feel mushy, it is likely that it is being over-watered. If the leaves fall off with a slight bump on the end, this is the early stage. In most succulents it is common for the stems to rot first near the roots. You will begin to notice the leaves shrivel from bottom to top. Echeverias are typically the most sensitive to over-watering. One thing to know about succulents is that they like to have their soil completely dry before soaking again.
Under-watering is a different story, since succulents are known to thrive on neglect. If the leaves start to wrinkle at the top, it is possible you aren't watering enough. But it is much easier to revive a dehydrated succulent than an over-watered one.
Note: the fatter the leaves, the less water it needs
How to care for an over-watered succulent
• Let the soil dry out completely before watering again. Succulents are capable of going days without water.
• Try spraying the base of the succulent rather than pouring the water in.
• Switch to well-draining cactus/succulent soil. It is possible the water is being trapped in the soil and creating root rot.
• If you see black spots on the stem, it is time to perform surgery. You will need to cut the stem and propagate it.
How to care for an under-watered succulent
• First and foremost, increase the amount of water you are giving. Don't increase it tremendously but water more consistently throughout the week.
• Using a clay tray, pour water into the tray and set the pot on top of the water so the roots take it in. Often times the roots don't receive enough water because we are only spraying the top of the soil.
Now that we've talked about watering routines, it's time to talk about soil. In order for the soil to completely dry, the water needs somewhere to go. Without well-draining soil, the water will be trapped and cause the roots to rot. In general, use cactus/succulent soil. I get my soil from Ashcombe Farm and Greenhouses because they already provide a soil mix for you that's great for draining and aeration! The goal is to provide aeration for the roots as well as drainage for the water.
The key to growing healthy succulents is sunlight! If you keep yours inside, place it by a window that receives sun all day. If you keep them outside, put them in indirect light because they will get sunburnt with the drastic temperatures.
Hopefully this helped you identify what's going on with your succulent and how to take action. These solutions are based off of experience and research so I'm confident your succulent will be okay :)