Please try this exercise to develop concentration. In Sanskrit it is called tratak, which means 'gazing'. First wash your eyes properly with cold water, not warm water or hot water. Then make a very small circle on the wall at your own eye-level, and inside it make a dot. It should be black, not blue or red or any other colour. Then stand facing a wall. There should be a distance of about three and a half feet between you and the wall. Focus your attention on the circle with your eyes relaxed and half open. The force of your concentration should come from the middle of your forehead. After three or four minutes, open your eyes fully, and then try to feel that your eyes have covered your whole body. Feel that from head to foot you are all eyes. Your whole physical existence has become nothing but vision. Then please concentrate on the dot inside the circle. Then you have to start making the object of your concentration smaller. After a few seconds try to feel that your whole body has become as tiny as this dot on the wall. Try to feel that the dot is another part of your own existence. Then you will enter into the dot, pierce through it and go to the other side of the dot. From the other side, you have to look back and see your own body. Your physical body is on one side, but on the strength of your concentration you have sent your subtle body through the point of concentration into the object. Your subtle body is now on the other side. Through your subtle body you see your physical body and through your physical body you see your subtle body.
When you began to concentrate, the existence in your physical body became all vision. At that time the dot was your reality. When you entered into the dot, then vision and reality become totally one. You are the vision and you yourself are the reality. When you look back at yourself from the dot, the process becomes reversed. Now you are the vision there, and the place to which you are returning is your reality At this time, again the vision and the reality become one. When you can see it in this way, your concentration is absolutely perfect.
If you can concentrate and go to the other side of the point you were calling reality, your whole existence will be far beyond the vision and the reality. The moment you can feel that you have transcended your vision and your reality, you have boundless power. You will be able to use this power of concentration for your spiritual life, for your intellectual life, while working, while cooking, while doing anything.
Excerpt from Meditation: Humanity's Race And Divinity's Grace, Part 1 by Sri Chinmoy.