My advice is not original; I've read this recommendation in books on the craft of writing.
It's this: Never, ever, talk about your work in progress with anyone but your writing confidantes, whoever they may be. You see, I believe that when you try to summarize your premise and plot, characters and conflict into two sentences shared at the sidelines of a soccer field, you squash the life out of your story. After all, the world of your novel-to-be is so much more. Furthermore, I am convinced that when you put it into words, some of the magic in your private fictional world escapes; the enchanted fairy forgets how to fly for an instant and the evil wizard is not as cutthroat as he had been in a writer's mind.
I agree with everything the others have said, so I'll share my super secret for success. I used it when I wanted to find the man of my dreams, have amazing children by a certain age, when I wanted to work on Capitol Hill, get that column in the Boston Globe, receive the call from a producer at NPR, and then catch the attention of both the agent and editor of my dreams: I visualized my success. I imagined every step, no detail was too small. It's like casting a spell, conjuring the four winds to spin your dreams into life. Imagine the possibilities.
The usual words of advice are to read and write. I find that only the platform from which you need to take your first step. My advice? Do small things to take yourself seriously, so others will take you seriously as well. Create a space that looks and feels like an Official Work Space; even if it cannot be exclusively yours, claim it in chunks of time as yours alone, not to be disturbed. Set deadlines you will meet, if not with a writers group then by telling one honest and good friend you plan to write 20 pages by month's end. (Or whatever.) Then do it again, and again. Read about writing, and take classes from teachers others recommend. If this is going to be a real career, even if you can't quit your day job(s), treat it like a real career, with intent and action.
The single most important advice I offer is to be positive. Focus on your strengths as a writer, as this will go a long way toward helping you recognize where your writing needs work. Stay optimistic that you too will get through the tough writing days; you will find an agent and get offered a contract for your novel. Be affirmative in your interactions with readers and writers and industry insiders; the world of publishing is a small one. Nice people finish first in my book. Express your feedback to members of your writers' group or about books you've read in ways that are constructive, encouraging and supportive. When you truly believe in yourself and your writing, you will treat yourself with respect. When you respect yourself--others will too.