My experience so far is that most as-yet-unpublished writers crave external validation. Obviously this also applies to other creative activities: the would-be actor wants to be cast, and then hear the applause of the audience, the artist exhibits at local shows and hopes their paintings are bought. However, people who take up acting or art as a leisure activity don't expect to be able to make a career out of it (although I'm sure a few harbour dreams of discovery). For most, the creative act in itself is enough enjoyment to continue.
There seems to be something different about creative writing. We know it is possible to develop a new career as a writer later in life, with Mary Wesley as the stellar example of a writer who was first published in her 70s. So publication becomes the aim, and often the sole aim.
I think that's a shame. Writing is how I make my living, and I have a love-hate relationship with it at times, but essentially I find it an endlessly fascinating process. Oh yes, the money and the fact that other people seem to enjoy my writing is very nice indeed, but I'd not be able to write if it was only about the money side, or external validation.
It has to come from within. I think all writers, published and unpublished, have times when they think their work is rubbish, tripe and utter drivel but somewhere deep down it seems worth carrying on, just for the interest of writing. You have to believe that your work, your creativity, is a worth while way of spending your time, and it doesn't matter what other people think. You have to be able to self validate. C'mon, people, all together now - because you're worth it.
(Sorry, couldn't resist...)