Never give up. Let's face it, not everyone will get published. Getting published takes luck as well as discipline. But finishing a manuscript? That's entirely up to you. If you don't get published, don't let it be your fault. You'll regret that. It's not failing to get published that should frighten you; it's knowing that it was your fault, and dealing with associated regret. If you do everything you can to make it happen, you should be damn proud, no matter how it turns out.
Never give up. Keep practicing.