This is one of the prime necessities for creative thinking and for healing. You must learn to concentrate all your thoughts on a subject of contemplation or an object in hand. One’s concentration should focus, like a magnifying glass, so that it becomes absorbed, unmoved by external forces, as to suspend the present-day self (attunement and at-one-ment).
Concentration entails focusing our attention completely on a subject, emotion, thought, or idea. The size is no matter; remember what Joshua said, "He that is faithful in that which is least is faithful also in much" (Luke 16:10). We need to develop the skill of concentration of such a degree that nothing moves us from our work.
There are no limits to how far we can extend our comprehension of the Divine Plan when we develop our ability to concentrate and observe.
On the subject of concentration from a Stoa Lesson by Daskalos:
If I have a magnifying glass and I concentrate a few rays of the Sun on a sheet of paper, it will catch fire. That's a phenomenon: concentration of the Sun rays through some means (the magnifying glass). Otherwise, the rays of the Sun are everywhere and we still feel cold. We have a cold Sun during the winter, yet a few of those rays can make a paper catch fire. Such is the Mind.
So, what's concentration and meditation? Using the brain. The material brain is used as a magnifying glass: concentrate a few rays of the Mind Supersubstance, and you'll see the result. And this means – knowing whatever you want to know by concentrating the Mind on these things. It's leading us to knowledge, and still more, and more. But, we have to find the way of doing it.
The secret, now, is to use the Mind in the right way. We are using it in the wrong way now, definitely! And how: by enslaving the mind to serve so many petty unbridled desires, from morning to night! Desiring, desiring, desiring, changing the desires and thus enslaving the Mind to this or that desire to serve this or that emotion. And you call that life? That is not life! That is the way that makes a human being unhappy. What is the right way of using the Mind? And, what will the Mind, by using it in the right way, offer me? What is it offering me now by using it in this way? You'll have to study this.
Using the mind in the right way means not enslaving it to serve the desires, the emotions and all the human expressions. What do I gain now by using it consciously. I can gain many, many things – well, everything. ~ DASKALOS