Answer: Christmas cactus will shrivel if it is kept too dry. Although called a cactus, it is not really a cactus. Instead, it is a succulent. The soil should be allowed to dry out somewhat between waterings; when you water, drench it thoroughly.
If the plant has grown much bigger or has been in the same pot for many years, it might need repotting. If you do that, use a well drained soil mix and move it to a pot that is just a little bigger. Another approach would be to root tip cuttings and start new pots of the Christmas cactus without disturbing the original plant.
This plant may also shrivel if attacked by mealy bugs. These can look like little white bits of fluff, often at the joints between a leaf and the stem. These can be dabbed off with a cotton swab dipped in rubbing alcohol.
I hope this helps!
Q&A Library Searching Tips