What Does It Mean to "Never Give Up"?

I've read some great comments on here and other blogs lately, writers supporting writers in the midst of publishing trials. A common theme is to "never give up". I've used the phrase myself (have a tag dedicated to it, as a matter of fact). But I got to thinking, what does that really mean?
What are we not supposed to give up on?

Is it the dream of seeing your book on the shelf? Some authors are perfectly happy with their eBooks being published and may never see their novels in print. Have they given up? Maybe that wasn't their dream.

Maybe the dream is to write professionally, as a career where you don't have to work another job, but can write instead. In the economy, some authors who had previously achieved this have had to find work (Sara Donati, for example). 

Maybe it's just that we're not supposed to give up on ourselves, whatever that entails. Don't give up the hope that you can achieve what you set your mind to, be it a novel in print, an eBook, a finished manuscript, a flash fiction piece, or even a full-time writing career. Whatever it is that you want, don't give up on getting it. Because giving up means you definitely won't get it.

Still, feel free to change your mind about what you want at any given time. ;)