There are no exceptions to this rule. It may sound harsh, but in order to finish a novel, you have to write every day. The only way to complete something as long and as strenuous as a full-length book is the day-to-day work of writing. It doesn't have to be much. Even if it is just a sentence or two. If you can say that you wrote for that day, then you have something to build on. It takes multiple days of building on each other to make a novel. Don't miss a day.
Many authors write without a plot in mind, and this may work for them. However, most authors need to have some sort of goal in mind for their character, or there is no story. Characters need to have a goal and be motivated to reach that goal. That motivation should be very compelling to the character. Of course, there should be some sort of conflict standing in the way of the character reaching that goal. If an author knows these things before she starts writing, it could save her a lot of rewriting in the future.
Resist the temptation to edit as you go. Allow yourself to write as freely as you can in the first draft and know that you can edit out any imperfections when the editing process begins. Most of the fiction writing process is done in the editing phase. At least there is something to work with if you can get your thoughts down. If you are stymied by fear of bad writing, then you have nothing to work with. Let the words flow, then whip them into shape on the second round.
A novel is really just a collection of chapters, and chapters are collections of scenes. Scenes can be further broken down into action and reaction units. They are a collection of how a character acts and then what the reaction is. Scenes have their own structure as well: a beginning, middle and end. Scenes reach a climax or disaster. It is worth it to the budding novelist to read books on the structure of story to get a feel for how books are constructed. Even if you are not someone who plots beforehand, it is vital to know how a story works for the editing stage.
Writing is a psychological journey. It can be difficult at times because it is just you against the blank page. The only way to write a novel is to remind yourself why it is important to you. Some people want to be published. Some just want to say they did it. Some can't help themselves. No matter the reason, write it down somewhere and go back to it from time to time. Remind yourself why you decided to write the novel in the first place. The middle of the book will be especially challenging. You will want to give up. Read your reasons why you want to write, and continue, everyday, to write your novel.