If you are on the app then the button for filtering flairs from your feed may not work.

If you navigate to the search function in r/cats you can manually exclude specific filters like so:

-flair_text:"loss"

This will exclude "mourning/ loss" posts from your feed.

If you want to exclude more than one flair type then you can add a second query after the first like so:

-flair_text:"loss" -flair_text:"medical"

Where each new query is added after a space.

The default sorting option is "relevant". You can manually alter that to "new" or "hot" should that be your preferred sort.