can you see the circles in this picture?

At first it is difficult. You might not even be able to do it. Then you might see them but they disappear quickly. But if you find them and keep looking at the picture your brain will more easily identify them and focus on them longer.

The same is true of focusing on your goal. It is there but difficult to identify. Or it might be fleeting.

After a while you get better at it and can stay focused.