Natural concentration is when the mind can hold a thought for a long time, when thoughts are under our own control.

With some meditation techniques, people are given ideas or mantras, which they often simply repeat. They do not penetrate the mind and do not bring any sense of meaning. People bounce these ideas around like a ball in their mind and, from the mind, the ball of thought is bounced to the mouth. Sound patterns are repeated, but nothing has really been understood. The result of this is that there is very little power generated from within to bring about change in behaviour, or personality. Thus, everything continues in the same way. In these cases, people are not focused on spirituality. As a result, after a while, such people find meditation boring, they fall asleep, or think that by repeating words, either verbally or mentally, they are doing meditation. However, the right type of concentration is not brought about simply by repeating sounds or ideas.
Natural concentration is when the mind can hold a thought for a long time, when thoughts are under our own control.
Without concentration the mind goes here, there and everywhere, jumping like a monkey from branch to branch, idea to idea. When there is a natural concentration, we can control our mind and there is peace. This one-pointed concentration on a thought, holding it for as long as we like, gradually collects strength in the mind and in the self.
A strong mind is a mind that is peaceful, stable, satisfied and can remain in the deeper meaning of a thought. There is no waste caused by over-thinking, or the high speed of thought. These are the two greatest diseases of the mind these days, which is why there is so much stress and mental breakdown.