I've read that it takes about a month to make a new routine into a habit, so for the last several years I've tried to tackle just one resolution, or part of a resolution (I break the big ones into manageable, measurable bites) at a time, beginning on the first of each month. So far that has worked well for me.
For this year I want to focus on gratitude and mindfulness. A friend on FaceBook actually made this suggestion, and I want to try it - decorate an empty jar and keep it where you see it every day. Whenever something good happens, whether it is a big thing or a small one, write it down on a slip of paper, date it, and put it in the jar. Next year on New Year's Eve or some other appropriate day (Thanksgiving?), open the jar and read the slips out loud.
Good luck on your exam - the best advice I can offer on that one is to try to study the material a little at a time. Try to set aside 15 minutes each day to totally concentrate on the exam material. And try not to do it the same way each day; reading, writing lists, drawing mind maps, and reciting material out loud all use different parts of your brain, so the more ways you can work with the material the more likely you are to remember it when the big day comes.