Over- and underwatering plants

• Overwatering plants can kill it as the stagnant water sitting on the plant causes root rot. But even then, you can save it. If you can see any green bits, you can cut those and try rooting them again.
• If you've underwatered your plants, resume watering and give them a few weeks to revive.

Don't be afraid to experiment with plants. Some trial and error will make it possible to grow some plants.