Using the wrong enclosure style
Trinidad Dwarf Tarantulas are fossorial, so long periods underground, closed burrow entrances and heavy excavation are normal for Cyriocosmus elegans. Build the enclosure around that lifestyle instead of using the same shape for every tarantula.
For Cyriocosmus elegans, adult size is about around 4–5 cm (1.5–2 in), but enclosure size should still follow the spider's current size. A sling does not benefit from being placed straight into a large adult setup.
Getting moisture wrong
For Trinidad Dwarf Tarantulas, maintain a modest moisture gradient, especially for tiny slings. Good ventilation and a drying surface are important. The mistake is usually treating the whole enclosure as either permanently wet or permanently dry instead of watching how the substrate actually behaves.
Keep fresh water available to Cyriocosmus elegans. Persistent condensation, a stale smell or wet substrate that never dries are reasons to reduce water or improve airflow.
Overfeeding or chasing a schedule
Feed Trinidad Dwarf Tarantulas according to size, appetite and abdomen, not because a calendar says food is due. Cyriocosmus elegans can refuse meals for normal reasons, especially around premoult.
Do not keep adding prey when a Trinidad Dwarf Tarantula is already very well fed. Remove ignored live feeders and offer food again later.
Disturbing premoult or moulting
When Cyriocosmus elegans shows premoult signs, remove live prey and leave the spider alone. A closed retreat is not an invitation to open it and check what is happening.
After a moult, wait until a Trinidad Dwarf Tarantula has hardened and the fangs have darkened before feeding. Larger spiders usually need longer than tiny slings.
Making maintenance too difficult
A good Cyriocosmus elegans enclosure lets you refill water and remove food remains without dismantling the main retreat. If every job requires moving cork, digging into substrate or working directly over the spider, change the layout.
Handling is not part of routine care for Trinidad Dwarf Tarantulas. Use long tools when useful and have a catch cup ready for rehousing.
Changing too much at once
Once a Trinidad Dwarf Tarantula has settled, avoid repeatedly rearranging the enclosure for appearance. Stable housing usually matters more to Cyriocosmus elegans than a constantly changing display.
If something needs correcting, change one clear husbandry problem at a time. That makes it easier to see whether Cyriocosmus elegans settles, feeds and uses the enclosure normally afterward.