You can set goals and make New Year's resolutions but you'll probably fail unless you remember one thing: stay conscious.
Let's say you want to lose 20 pounds in six months. That meets all the usual criteria for a good goal: realistic, specific, and important. But you will fail unless you stay conscious of the importance of your achieving your goal, from the moment you start thinking about eating through the moment you finish or get distracted by something else. Without that vigilance, it's just too easy to succumb to "Ooh, that food will taste good." It may also help to break your goal into a small step:one pound in the next four days, for example.
Another example: You want to land a job within three months and, to that end, you want to put in 30 good hours a week. During those 30 hours, you must stay conscious that you must put in the time, reminding yourself of all the benefits you'd get from landing a job. Again, it can help to break it down into smaller goals, for example, I'll make five calls today.
If staying conscious isn't enough, tell one or more people your goal and deadline and, if necessary, ask if you could check in daily. For example, ask if you could email them the letter grade A through F you'd give yourself for your day's work.