TiddlyWiki is a very flexible, customisable system that puts you firmly in charge of your own data. Every care is taken in TiddlyWiki's development to ensure that it is a safe place to preserve your most valuable data but the ultimate responsibility to reduce the risk of data loss falls to users.
The best way to make sure that your data is safe is to practice a rigorous system of backups:
* Consider using services like Dropbox to continuously back up your personal data to the cloud
* Retain backups before upgrading to a new version of TiddlyWiki