It depends on your overall motivation and ambitions in that particular field. I don't know which goals you have in mind, but let's take physical ecxercise for example.
If you are very motivated and ambitious in say lifting weights, and you want to e.g. Deadlift 600 pounds, you will need lots of discipline to reach your goal. You will have to set up specific plan, some milestones (400 pounds - 500 pounds - 550 pounds) and then work hard on achieving your goal. If you have the right determination and motivation, you should never change the goal. You should either reach it or die trying, as they say, because if you don't the failure will keep bothering you...
On the other hand, if you are not really motivated and ambitious in weight lifting, but just want to be somehow stronger, who really cares? Set up your goal at 500, then lift here and there. Maybe you lift 300 with ease, maybe 400, that's good enough, keep lifting for fun, skip when you don't feel like to - you still stronger than 95% guys out there, you've reached great results...
Another good way is to setup sort of general goal. For example, in stead of being focused on lifting 500 or 600 pounds, your goal is to "lift 3-4 times per week for most weeks of the year". Then you just lift 3-4 times a week, you can have lots of breaks when you don't feel like to going to fitness, you can lift light or heavy - but as long as you are lifting you are reaching your goal and more importingly - you are keeping fit, year after year...
The same can be simply modified with e.g. Girls. In stead of having goal "sleeping with 200 girls in 2 years", much better approach might be to have a goal "Go out 3-4 times a week for most weeks of the year and have fun with many girls". All you have to do then is to keep your schedule, go out and have fun 3-4 times a week. You won't be stressed about not reaching specific goals, you will focus more on fun in stead of getting the number (200) down, you will be more relaxed - and as a result you will gain lots of experience and thus great potential to sleep with many girls...
