Your question is not an easy one. All that we can state with certainty is what we learn from the Qur’an:

 

Man in Islam consists of body, mind and soul.  Even as our physical muscles can be nurtured and strengthened, likewise, our mental and spiritual muscles can also be strengthened through appropriate works or exercises befitting each.

 

Just as the outer world of senses is complex and diverse, the inner world of spirit and consciousness is also complex and diverse, if not more. The Qur’an teaches us that the soul is what makes us human; it is also referred to as nafs, although both words have various dimensions and propensities.

 

Human beings have been endowed with souls; they have innate inclinations towards good and inclination towards bad. And those who foster the good will succeed and those who foster evil will perish.

 

The soul in man is from the breath of the Divine; as such, it is immaterial.

 

On deeper reflection of the Qur’an, spiritual masters of Islam have told us that even as the material world has its traps, snares and dangers and it takes practice to navigate and explore the world of senses, the mysteries of the spiritual world are even more complex; so to navigate this world without the light of revelation and authentic spiritual manual will expose us to dangers. Devils are waiting at every turn to deceive us in the spiritual world. Therefore,  those who seek to explore this world independently of the guidance of revelation are at  best projecting their own subjective experiences as truths or representations of realities; or stated differently, they are projecting their own ego and devilish whisperings as authentic spiritual experiences.

 

Ekhart Tolle is a practitioner of the so called New Age Spirituality; for sure he has drawn on the spiritual insights of various religious traditions; however, one cannot rely on them.

 

If you wish to acquaint yourself with the Islamic perspectives on the mysteries of the soul, you should study the works of Imam Ghazali; his masterpiece Ihya is an encyclopedia of Islamic ethics and spirituality. If you don’t have the patience to engage in a deep study, you should at least consult his book translated in English as The Marvels of the Heart. It has been translated and published in England with an excellent introduction by T.J. Winter who is a scholar of Islam from Britain. Here is the link to it:

https://www.amazon.com/Marvels-Heart-Science-Religious-Sciences/dp/1887752315

 

Eckhart Tolle is not an authority or spiritual matters; he is rather more like a proponent of New Age Spirituality. Since it is not based on revealed Law and spiritual method, one can only read such works with extreme caution. For sure, he has drawn from insights from the spiritual wisdom of various religious traditions; however one cannot treat his explorations into soul, spirit and consciousness as though they were authentic. At best they are his subjective experiences.

 

One may follow scientific methods of practicing mindfulness. While engaging in these exercises a Muslim should chant the names of God or dhikr instead of using dubious expressions and phrases derived from the pagan traditions.

 

Muslims throughout centuries have developed spiritual mindfulness through diligent practice of dhikr.  There is no need to make it complicated; once we condition ourselves to focus on dhikr and trust in Allah and seek His help, He will take care of the rest for us. Allah says: “Lo! It is only through celebration of the Remembrance (of God) that hearts can rest in peace (or stated differently) attain a tranquil state.” (Ar-Ra`d 13:28)