In the Mahabharata Arjuna is being taught archery by his guru(teacher) along with the other Students.
The guru Dronacharya hung a wooded crow, from a tree branch and then summoned his students. Telling the students to aim for the crows eye but first to explain what they see. The first student approaches and the teahcer asks the student "What do you see?" the student says "I see the garden, the tree, the flowers, everything!" The teacher asks the student to step aside and not to shoot. He asked the next student and was told something similar "I see the air and leaves blowing in the wind.." The guru Dronacharya asks a few more students and they all have similar replies.
Then came Arjuna, when Arjuna was aksed what he saw he said "The only thing i can see is the crows eye". Guru Dronacharya said "Release your bow" and Arjuna hit the crow in the middle of his eye.
I hope that with a little reflection you can see how powerful yet simple that story is. Use it next time you need to focus.