Lots and lots and lots of people dream about writing a novel. Fewer people actually start. And fewer than that actually finish.
Writing a novel takes hundreds of hours, the ability to tune out distractions, forcing oneself to buckle down when the novelty wears off, and the mental perseverance to keep going when doubts and the am-I-crazies creep in.
There are lots of things that can stop someone from writing. What keeps you going?