A burning desire to fly is one of the biggest advantages you can have when applying for military aviation; sounds like you have that, so remember your aim as you go through the selection process.
Strange as it may seem, some of the people I met flying in the services didn't really care too much about the aviating part of it, amazingly to me, but there you go - they applied for one reason or another and made it through.
Good advice from giveitsome; focus on the job at hand now and don't worry about not making it, but if it doesn't come off, remember that a knock back from the defence forces is just a minor setback in the grand scheme of things.