Years ago I started a family tradition in my household of a meeting in which we decided what we wanted to accomplish, both as a family, and as individuals. And one thing I stressed is that you can never accomplish anything if you only resolve to do it. Accomplishment takes action. If you have goals toward accomplishment, the only way to achieve them is through action.
One way to make sure that action occurs is to write down what needs to be done to achieve the goal. For example, if your goal is becoming a better guitar player, one way to achieve this is to actually practice. Set reasonable goals for the number of minutes you'd like to practice each day, or each week, then make a chart with boxes you can check off. Let's say my goal was to practice thirty minutes a day, every day of the year. In its simplest form, you could use an already printed calendar and just write down how much you practiced on each date. If you want to have a chart dedicated to guitar practice, you can design your own with any number of spread sheets, word processors, etc. You can make it as elaborate as you want, but continue to keep in mind the original goal, to become a better guitar player.
When you keep in mind the original goal, whether it be guitar playing, fitness, or any other goal you might have, it's best to focus on the long-term. This allows for occasional lapses, such as, in our guitar playing example, missing a day. We may have goals, but sometimes life gets in the way and we miss a day or two. That isn't a time to throw our hands in the air and exclaim "I'll never achieve this goal", but a time to reassess and/or recommit. Often we can make up things like practice time by doing double the next day, or adding ten minutes for several days, but that's not even really crucial. What's crucial is that when we miss a day, we get back on the path and practice the day after that and keep going. Your ultimate goal is to become better, and you will. A few years ago, due to the large amount of donut buying that occurred at my place of employment, I made the goal to not eat any more of them. At the time, it was more of a New Year's resolution, although taking it one day at a time is what helped me keep that resolve until July. I mentioned to a friend of mine that I had failed at my goal, and he told me that no I hadn't, because I had succeeded in not eating any donuts for seven months. Till this day, I have had more control over what I eat, and likely, because I found out it was possible.
Actually, it rarely matters whether you set such goals for the new year or whether you start them at some other time. However, the new year does provide a natural break psychologically and that can be a great time to initiate new approaches, new goals, and new ways to accomplish your desires.
The key thing is to forget about the resolutions and make a plan to accomplish all you wish to do.