I'd like to find a Mac tool that kept a safe copy of the contents of textareas. Any idea?

Many many many times have I lost contents for example on Facebook. I’m writing a comment, or a message, and then I post and there’s an error and I lose all that I wrote.

I started a habit of selecting and copying the text to the clipboard and only then posting, just to be safe, and it’s effectively saved me a few times.

Now I thought it would be tremendous if I had a tool setup on my Mac that would monitor input fields and keep useful backups of them. Kind of a keylogger I guess…

What would you suggest to automate this safeguard?

Thanks!