My initial motivation, independent from feedback or appreciation from the folks around me or on the Interwebs, comes from really wanting to tell this story in a (relatively) unique fashion. Everything's been done before and there's nothing new under the sun, of course - but designing a story, characters and art style that's really YOU - I find that this is highly motivating. There's plenty of lookalike stories out there - there's plenty of readers looking for something weird or different, even if it's far from perfect. Perfection is pretty boring, anyway
Also, I really immerse myself in the minds and hearts of my OC's, often writing associative texts, poetry or 'automatic writing' to find out who they are and what they want. This can be motivating because they become more than just vehicles for the story - they actually push the story along.
However, if no one Out There actually enjoys what I create, or gives feedback and appreciation, I tend to get quite frustrated.
But taking it slow and letting myself be inspired by other creator's awesomeness (and hardships) keeps me on track. Also, I really appreciate the comments I get!
Hope this was of some help to thee <3
This does relate only to my current, long-term webcomic btw - I've done plenty of other short comics before, but really having the time to work on this story, create lavish pages and not squish 10 panels into one measly black-and-white page is very liberating!