There are two ways to meditate. One to strengthen the mind the other is to cleanse the mind. The first is the most common one found in all types of religions and other practices but it is only in the Buddha Dhamma that the second method is found.
You can strengthen the mind by learning to focus on anything (such as focusing on your breath, concentrating on a body of water, light.. etc), so following a thought process can do that in time. But to cleanse the mind one needs to understand a few things and go beyond the boundaries simple understanding and gain absolute insight into the thought process which occurs in one’s own mind.
One must understand the three qualities that keep us bound to this material/Immetarial plane which are Raga ( the attractive or adhering property of the mind), Dvesha ( the opposite of attraction which is the repulsive force) and Moha ( which is the illusion of understanding the world by the mundane mind which feeds Raga and Dvesha which in turn feeds Moha which is similar to a dog chasing it’s own tail ).
In the process of adherence of positive or negative thoughts(Rage, Dvesha), the emanation from the mind is unclean as this is not the absolute insight of the world as it is. This can be clearly understood as what one person desires, another person does not. Because what one person see’s as a repulsive force the other person may not..etc
One looks at all thoughts that enter the mind from the five senses (Externa) plus the archives and accumulated thoughts of the mind (Internal) itself and identifies them as a Raga or Dvesha thought and immediately stops from pursuing them any further. At the same time, one fills one’s mind with veetha-Ragi or veetha-Dvheshi (the opposite of Raga, dvesha) thoughts accordingly. In this way the mind STOPS from being a collecting point of GARBAGE thoughts which clutter and dirties the mind.
Raga springs from attraction of any kind, be it LOVE, lust, greed, wanting etc. veetha-Ragi thoughts are ones that immediately break down the source of the Raga thoughts into components and understand the ever decaying continuous process which is a common inherent property of the Universe. When we love someone and wants to “be with”, “marry”, “be happy together forever” etc. and the at the end of each of those paths there is sadness, unhappiness, woe, etc. one has had a thought of Raga. By understanding that one cannot hold onto anything at all in ones mind one can train not to get ATTACHED to anyone or anything. It is the attachment that causes all these problems. We are even attached to anger, hate, rage etc. That is why some cannot forget even after many years.
Dvesha is the opposite of Raga and are bound together like the two sides of a coin. If one exists the other does too. They may lie hidden and unseen, but they are there. The moment a Dvesha thought is identified one must immediately start the process to eradicate the negative thoughts by thinking thoughts of meththa, veetha-dveshi, which are thoughts of goodwill to all living beings equally. The ultimate way of doing this is to form an Adhishtana in one’s mind that oneself and all living things may attain the four states of Magapala (Sothapanna, Sakadagami, Anagami and Arahath).
After either of the above, one must look at oneself and understand that all these useless thoughts and actions are for a minuscule moment in time, be it the moment of thought or ones entire lifetime itself. By deeply understanding these, one can remove one’s thoughts from Raga and Dvesha which will be a practicing process itself. When one clearly sees the absurdness of Raga and Dvesha the need for such thoughts will dwindle over time,first taking some time but as one progresses along the path will/can happen in an instance.
If one can overcome Raga, Dvesha and Moha ultimately one becomes an “Arahath”- one who has overcome the 3 bonds. By this process, the mind is automatically strengthened too. But if one follows certain train of thoughts and let the thoughts in to feed existing thoughts one strengthens the mind be it good, bad or useful. Yet all kinds of thoughts are collected and focused in the mind. In the cleansing process, there is no adherence to any thought or process therefore no collection of thoughts or anything. Only an emanation of good thought energy from one’s mind.
The above process of excluding Raga, Dvesha and Moha thoughts and including Veetha Ragi, Veetha Dveshi and Veetha Mohi thoughts is the process called Ana Pana Sathi Bahavana. What the world believes as the Ana Pana Bhavana which concentrates on the breath is called Prana Yama which is NOT a Buddha Dhamma Meditation. The true and correct Ana Pana Sathi Bhavana is about the Thought process and not about concentrating on the breath.
So, the path of cleansing the mind is the way of the Buddha Dhamma and strengthening the mind is the way of the rest of the world.