Brian Tracy is the author of a very powerful book called Goals! I suggest you read it. In it he states, "any goal not written down is just a wish." How many times have you said you were going to lose a certain amount of weight? Just stated it, without writing it down, formulating a plan, or periodically measuring your progress. Well if you never have written it down you also probably did not reach the goal and you are not alone. The majority of us will never reach a goal unless it is written down in the present and personal tense with a timestamp on it.
For example here is one way to write a goal down, "I will lose 20lbs and weigh XXX on the Friday of Memorial Day Weekend."
Please consider the following when deciding on a goal.
1. Make sure it is a realisitic and motivating.
2. Make sure you have a safe, effective but flexible plan to achieve it.
3. Periodically measure your results along the way. I suggest 2x weekly.
4. If there are setbacks, accept them and move beyond them. Use a minor setback as an opportunity to leap foward.
5. Frequently review your goal and plan. In the face of new information, is the goal realisitic? To simplistic? If so, rewrite your updated your goal and plan. then continue on to success.