The single-minded Fisherman/ Concentrated Sadhana

What does it mean to be single-minded? I will tell you a small story: Once there was a fisherman sitting on his boat, on the river bench actually, throwing his bait inside the river and there he was waiting for the fish to eat the bait. The focussed that he was, he was just looking at the bay, well at the floating, when he was sink inside. He knew there were a lot of fishes around. A stranger was passing by and said to the man “Mr., can you tell me where Mr. X stay?” He was too concentrated, no answer. Second he repeated again this question one time, two times, three times -no answer. This stranger really got angry and walked his way. As he was walking away, the fisherman was very satisfied...he saw the floating go down, he pulled and caught the fish. Then he called the man and said “Hey, you were calling me. You were telling me something. Tell me. What were you telling me? What were you asking? “Then the man, the stranger said “I repeated my question several times to you, but it was as if you didn’t hear me or see me. Why should I repeat it again?”
That was one-single mindedness, focus. When you meditate you can achieve this state. When you do your sadhana, you can achieve a state, where nothing can disturb you. No left, no right. No hearing, no seeing, because in the deepness of meditation or deepness of your practice, you have to really focus. But if you are not disciplined with yourself, do you think you will have this focus? No, this is where everything get’s uncertain. You will do prayer and you will be very superficial, because you are not satisfied with yourself. With self-discipline you have to work for it. It’s a purification of the mind and senses.