Usually happens in increments and not all at once. With each awakening, a mind unwind, and a re-identification with essence or pure consciousness. The 'I am' grounds itself, and there's less of I am this, I am that. Ego and mental constructs soften up.
Awakening is also a form remembrance, that's why the Sufi's practice Zikr, Zikr literally translates to remembrance. In realization, we remember what we're made of or who we are. It's that simple.
There are many forms or manifestations of awakening or realization, and that's because each bodymind is conditioned in a certain way. So the way one experiences realization may differ, but the truth itself, the feeling of it, is always the same.
With that in mind, here are a few examples of how realization might appear:
Emptiness, which feels like the mind is turned off and there is no one there but the witness of all experience. Silence takes over, and due to this silence, one rests in razor sharp open awareness, in blissful darkness. Think a deep meditative state.
Unity, which feels like all of us humans are connected and one, and there's this feeling of beauty and openness, similar to watching the sun dip into the ocean and having that moment of a deep inhale and long exhale. A moment of deep connection.
Oneness, a feeling of deep and unconditional love, and knowing that this deep cosmic love powers and unites the universe. I find unity to be more local, here on earth, and oneness to be on the cosmic side of the spectrum.
Expansion, as in the witness expands and all objects reside within this dark stillness. Not dark as in evil, dark as in vast and colorless.
Connection, personal yet impersonal, so a feeling where you and your partner or anyone you love become one. Love transcends the personal aspect and yet remains grounded in the bodymind. Essence recognizes itself.
A chakra opening, so the heart chakra, or any other energy center north of it, can open up, and there could be a feeling of love, connection, unity or creativity.
Presence or the Now, so this moment right now, could feel like eternity. Its as if this (ancient yet absolutely fresh) now is the only thing that's real, and we as human beings keep passing in and out of it. So past and future are nothing but mental constructs i.e. Jesus never left, he's here and now manifesting through us and in this eternal now.
Wholeness, a space where one feels empty of all desire and fear and all that remains is a wholeness like no other.
Love, or divine love, a feeling of a pure, deep, tender, indescribable love could be felt or known. A love that is undoubtedly way beyond the bodymind. Someone like Rumi was well acquainted with this type of love, you can feel it in his poetry, the madness of lover and Beloved.
A kundalini awakening, energy shoots up the spine, past the crown chakra, and one experiences absolute unity and love. This usually is an intense and unexpected experience that causes a serious shift in consciousness (or one could go mad).
So that's how awakening might unfold, but why does this happen ? How does it happen ? And how does the awakening journey unfold ? I find these questions to be so interesting, and I'll try to answer them from my own experience.
Why does it happen ?
It happens because pure consciousness wants to experience itself via the bodymind. It's like the truth wants to breakthrough. The formless wants to experience form.
'I was a hidden treasure; I loved to be known. Hence I created the world so that I would be known' - Old Sufi saying, not sure about the origin, but Ibn Arabi uses it often.
From the perspective of the soul, 'soul' being the entity seeking the truth, reality or home, it happens because of the following reasons ... Sometimes it just happens, out of nowhere, other times one consciously seeks it hoping to find peace or love and end the cycle of suffering.
For it to happen out of nowhere, I figure one's karma plays a big role. So the soul purifies herself for quite some time, and if its meant to happen ... boom, reality reveals itself, and the soul dissolves into her essence. I figure prophets and sages belong to this group. Look up someone like Ramana Maharishi, that's a good example. These massive awakenings are so interesting and one can only wonder at the how and why.
Awakening can also happen when one goes through a devastating trauma. The suffering can be so deep that the only way to escape it is to wake up, and so it happens, a movement of grace and/or karma.
It's all grace and/or karma I guess, but the way they manifest differs from one soul to the other.
The more traditional path is one where a person hears something about awakening, and it resonates, and the seeking begins. What's funny here is the ego begins the journey thinking this will happen to 'me', and so the seeker waits for the awakening/fireworks to happen, and nothing happens. So many failed attempts eventually humble the ego, and this is when reality might begin to reveal itself. A spiritualized ego is so tricky. In retrospect, one smiles and thinks, what a moron !
How does it happen ?
Either an ego death, and one remains with what remains. Or, as mentioned above, small openings or glimpses here and there that push the soul higher up the ladder. Higher up the ladder doesn't sound right, there's no ladder, but you get it. Let's say with each opening, a bit of the ego dissolves, and one feels a deeper sense of presence.
The Sufis for example talk about states and stations, or Haal and Maqaam. So a state is a glimpse past the veil, and a station is permanent way of being. The journey is a mix of both states and stations.
How does the awakening journey unfold ?
At its own pace, this cannot be forced. This is a mystery that we will never be able understand. All we can do is let go, and live moment to moment. Letting go means having faith in god. We open our hearts, do our best as a humans (serve) and know that the universe has our back. In arabic they say i'qal wa twakal, meaning, humble yourself and surrender, or just try to be nice to people and have a good time playing this game we call life.
Finally, this journey has no end, and this is what makes it so beautiful, interesting and utterly mysterious.