First Saturday of the New Year!
This is the perfect timing to backup your Mastodon data!
HOW TO
From the web interface:
1. Go to "Preferences" > "Import and export" and in the "Export" section click on "Request your archive" at the bottom
2. Wait for the compressed file to be ready, it can take a few minutes. You might receive an email notification if you have set it up that way
3. Once ready, in the same section click on "Download your archive"
(I like to save mine in a local folder I name "MastodonArchive_YYYYMMDD") 
4. Then, in the upper section of the same page click on each of the "CSV" buttons you see on the right side and save them in the same local folder
5. Magic!
Note: You should probably do this more than once a year too 