Have you had your form checked? A TSR reviewer can have a look at it for you and give you feedback. If the form is the best you can make it then there is no point in not submitting it. Choosing not to just means you have decided (by default) you no longer wish to go to uni. If you are worried about not getting on, then be realistic in your choices, but the risk of soemthing not turning out the way we would like is the risk everyone takes.