Q.What Is Wrong With My Jade Plant? It Seems Like Not Thriving At All.
The leaf just fell off. I watered it a couple of days ago. I make sure the soil is dry before watering it again.

Certified GKH Gardening Expert
It is likely a watering problem. The articles below indicate a shriveled leaf that drops may mean not enough water, although people usually tend to overwater their succulents. Take a look at how you are watering according to these articles:
https://www.gardeningknowhow.com/houseplants/jade-plant/jade-plant-care.htm
https://www.gardeningknowhow.com/houseplants/jade-plant/limp-jade-plant-help.htm
https://www.gardeningknowhow.com/houseplants/jade-plant/pests-of-jade-plants.htm