All negative comments at the time of writing, so I'll go first - the jokes I remember where quite funny to me. Not rofltrain, but on thr spectrum of funny none the less.
Chuck Norris does not turn on the light, he turns off the darkness.
I realise this is an older thread, but it could be caused by deleted files not being released by the application - a reboot or killing said application would help. Can be checked with
sudo lsof | grep deleted
It can also just be corrupt metadata about a file where a small file is seen as taking up some ludicrous amount of storage. This thought was triggered by you mentioning the thuderbird sent directory. Inspect the files there.
The only reason we're both stuck at the same light is you.