Even the greats started out bad. Consistent hard work and repetition is the only way to become better at anything, and key to that is developing the right habits.
Beat the sun up and get typing while everyone else is asleep. Finish work and get writing. Lock yourself away and get your arse in the seat, and write some more when it’s the hardest thing, then suddenly the easiest thing, in the world. Don’t be a writer who loves to be seen writing; be invisible. That’s when the best words come.
Don’t be known for the quality of your writing; be known for being the hardest worker people know. When you do that, the quality of your writing will grow anyway. Your writing skill is a muscle, and it can be trained.
The most important thing to look at first is how you’re thinking. If you tell yourself constantly that you’re not a good writer, then that will be your permanent state. If you’re convinced that you’re not yet worthy of attempting a novel, then you never will. Remind yourself every time you sit down at your computer that every writer you idolise had to start out bad at some point.
Remember: talent is a myth. Practise is all there is.