I think that's incredibly liberating! You can sit down today and start being a writer. Yes, it's also a little scary--especially when you're staring at a blank page or a blinking cursor and wondering, Can I really do this? Obviously, though you don't need much to start, writing a novel is a very complicated, long-term endeavor. That's where the other meaning of "practice" comes in. It's ok if you start out terribly, and hate everything you write; as long as you get a little bit better each day, with each chapter you write, and with each revision you complete, you'll get there. You'll fall in love with the process, which is the only way to keep yourself committed.