Seriously, go around and tell people that you want to write a new york times best seller and see what kind of reactions you get lol. Talk about destroying your motivation quickly.
Having people sincerely wishing you the best, congratulating you on your initiative and dream-chasing tends makes it feel like you're doing something positive. All you've done, however, is talk about it and are already getting rewarded. That undermines real motivation to start/continue far too easily.
Let those rewards come naturally and from within with actual progress.
Then I shut up about it, and actually got in shape. And when I ran into some people who I rarely saw, and they were shocked by my 40+ lb weight loss and how good I looked, I got that same emotional reward but also the actual reward of being in shape and being able to do the things I'd only imagined being able to do.
Now I discuss what I'm doing with some like minded friends and we keep each other accountable (Hey, how's the running going? Made it a full 10k yet?). But I don't discuss it with other people in general unless it's brought up by them. A kind of happy-medium between the talk-too-much and just-shut-up-and-work modes of operation.