This step is often missed in the process of goal setting. You get so focused on the outcome that you forget to plan all of the steps that are needed along the way. By writing out the individual steps, and then crossing each one off as you complete it, you'll realize that you are making progress towards your ultimate goal. This is especially important if your goal is big and demanding, or long-term. Read our article on Action Plans for more on how to do this.
Achieving complex and difficult goals requires focus, long-term diligence and effort (see Goal pursuit). Success in any field requires forgoing excuses and justifications for poor performance or lack of adequate planning; in short, success requires emotional maturity. The measure of belief that people have in their ability to achieve a personal goal also affects that achievement.
Assess why you're slipping: are you not sticking to your plan, or is your timeline unrealistic? If it's the latter, adjust your plan to something more reasonable. If it's the former, work on dedicating yourself to sticking to your target. Sometimes our plans are thwarted by outside influences, about which there's not much you can do; simply reorient yourself and continue onward. Keep in mind that failure is a part of progress.