Firstly think about your time availability. Realistically how much time do you have available to you for the completion of this dissertation? An academic term can seem like a lifetime but in reality it is probably about 12 weeks. There are 168 hours in a week. Take away the time you need for sleeping, eating and other elements of daily living and see what time you have left. It will probably be between 6 and 8 hours. Now think about the other demands on your time. You may find that you have other assignments to complete for your other modules, other lectures to attend and seminars to participate in. With a dissertation you cannot simply decide to priorities by deadline.