Setting goals is one of the most important skills you can have as an athlete. But setting goals is sometimes harder than it sounds. If the goals are too easily reached, they can actually hold you back instead of motivating you to move forward. If the goals you set are too difficult they can seem unreachable and discourage you. Many people recommend setting a big, very difficult to attain main goal, then setting smaller sub-goals that will happen along the way to focus on as you move toward achieving the main goal.
If you are setting a goal for your 2k time on a C2 rower and your current time is 9 minutes, your main goal might be 7 minutes. You might set up sub-goals of 8:30, 8:00, 7:45, and so on clear till you get to your main goal of 7 minutes.
But I think setting sub-goals that are slightly different in nature from your main goal works even better. It works better because it give you a bit of mental variety and a periodic break from ALWAYS focusing on the same old thing. For instance when a beginner weightlifter decides he wants to snatch 100 kg, he might set his first sub-goal as a 100kg snatch deadlift. Obviously you will need snatch deadlift more than 100 to do a 100kg snatch but it is a nice first step. The second sub-goal might be to back squat 150kg. A 150kg back squat also does not guarantee the ability to snatch 100, but the snatch deadlift and the squat are strength levels that have to be met and surpassed on the road to a 100kg snatch. Other sub-goals could be meeting a certain number with the snatch from the hip, or power snatch.
The real trick is to pich sub-goals that are different than the main goal, but not too different. Different enough that they give you a mental break but not so different that meeting the sub-goals does not move you toward your main goal.