This is a Sufi saying, that the heart is the veil to the soul. In this mystical path, our heart is where we store our feelings and opinions that have been formed in this life. It separates our lesser ego, the Nafs, from our Soul, the essence of God. The work of the Sufi, or any mystic, is to cleanse the heart, making it pure and clear, so we in our human personality can see our own Soul, and thus God. This is to know your Self.
In order to see the soul, we must lift or see through the veil. This veil is clogged with dirt and gets denser and denser due to our actions and the formation of our lesser ego. Every regret, guilty feeling, negative emotion, resentment, anger, jealousy, bitterness etc, is dirt on the heart. This may sound like an impossible mountain to clean, but in fact, it is not that difficult. Even the densest layer of mud will wash away quickly with enough water.
By removing the ego from making selfish decisions, we cleanse the veil and thereby can see though it to the soul. Our qualities of character and moral conduct are what counteract the negative aspects of the ego. Effectively, good qualities cleanse that density which is clogging the veil and preventing the light of the Soul from shinning through for us to see.
Who are we to see the soul if we are not the soul?
The Soul is the spark of divine light that is, one may say, our true essence of what we are, what keeps us in existence. Then we must ask, who are we that is existing due to this Soul?
We are the individualised thoughts that have come to be a person which is held together from the experiences of life to life and the power of the Soul. The individual person can be compared to a dust ball, the bunch of threads, dust and hairs that collect under the bed. If you take apart the dustball, thread by thread, there is nothing left. All its parts are held together by static electricity. The power that holds all the experiences together to form your individual being is pure energy that is not individual, but rather, Universally One.
As the sun holds the planets through its gravitational force, the Soul holds our thoughts and experiences which have formed our ego and heart, which is the veil around the Soul. That spark of divine light holds with the power of spiritual gravity all these things within its orbit, but by so doing it restricts us from seeing itself because our consciousness is always on the outer layers of that veil constantly seeking new adventures, possession and experiences, not the inner layers seeking its source.
Our deepest hopes and aspirations are on the inner layers, closest to the soul, which is why they are vague and difficult to materialise. The many layers of that veil stand between the soul and the conscious awareness of our mind which is subject to all the fragmentation and distractions. And so we may get glimpses of the deeper layers of the veil, but cannot activate or actualise them.
We are merely those thought forms and opinions which are our reactions to events.
When those thought forms or ego have been eliminated or cleansed of their dark density and the veil to the soul becomes transparent or clean, the heart, then those individualistic parts of the ego which make you you, are cleansed and the soul can shine through clearly. Individualised thoughts, fragments and memories, which are those things which separate each of us from each other no longer hinder us. This is how individuality vanishes and unity is attained while you remain who you are, but pure of heart and mind.
With that unity there is no need for individuality and separation, but consciousness of your individuality does not vanish because we have attained unity. By virtue of eliminating those things which are the negative aspects of your personality you become open and objective, not annihilated.
As you seek to attain that unity, those very desires for that unity are creating and attracting more density in the ego which by their very existence prevents the clarity and cleansing of the heart and therefore prevents the unity from being attained. Simple presence, awareness and open-minded consciousness of the present moment will break fixed opinions and is the method of attainment.