In writing, balance is crucial, both in story and yourself.
A novel needs balance. It can't be too weighty on character, description or plot, otherwise things start to get complicated. Unless you are a proclaimed literary genius (Charles Dickens for description, J.D. Salinger for character etc.), there is no way you will get away with this. Also, things like plot holes, grammar flaws and general messiness in your manuscript are a lot easier to spot than genuine talent.
Balance is also key as a writer. Writing is tiring. Coming up with the right words, the correct scene, best dialogue and making a novel flow is hard work, and you have to know the difference between 'if I keep writing I'll get through this' and 'if I keep writing all I'll end up with is babble'. While it can be motivating to set yourself a deadline, it can also be restrictive. Putting things like deadlines and targets on writing can hinder you, and it can be even more frustrating when you don't meet them.
Keeping balance between these things is hard, but if you do, your writing will be a lot better for it. Sometimes it's easy to keep this balance, and sometimes it's the hardest thing in the world. You've just got to know your limits, and always have the determination to be better. I don't know how I would write without them.