The nature of spiritual love
When the attractive qualities of the "object" of affection
continue to exist and become even stronger,
and one continues to have association with the "object" of affection
then the affection grows and becomes attachment.
This attachment becomes part of consciousness (e.g. Krishna consciousness).
According to Transcendental Knowledge, consciousness is the seat of attachments, beliefs or love.
Spiritual love is the intrinsic nature of the soul.
It is awakened through the practice of sadhana-bhakti,
as Rupa Gosvami writes in Bhakti Rasamrita Sindhu
kṛti sādhya bhavet sādhya / bhāvā sa sādhanābhidhā
That which is done to realize the goal (of life) - kṛti sādhya sādhya
which is (known as) the state of awakening of spiritual love - sa bhavet bhāvā
is named the practice (of spiritual devotion). - ābhidha sādhana
Krishna Das Kavi-raj Gosvami writes in Caitanya-caritamrita (Madhya lila 22.107):
nitya-siddha krishna-prema sadhya kabhu naya
shravan-adi shuddha-citte karaye udaya
The eternal and perfect love for Krișna - nitya-siddha prema kṛṣṇa
is not something you can get (it exists in the unmanifested state in the soul). - naya sādhya kabhu
Beginning with hearing (about the games of the Transcendental Lord) - ādi śravaṇa
the consciousness is purified and (love) awakened. - citte śuddha karaye udaya
The meaning is that when the soul is purified from the covering of material attractions,
it attains the state of pure virtue - shuddha sattva,
and in this state, while practicing saddhana bhakti,
beginning with hearing (shravan -adi) about the plays of the Transcendental Lord,
the rays of love appear "on the horizon of the heart", as also described by Rupa Gosvami in the Bhakti Rasa-amrita Sindhu (1.3.1):
śuddha-sattva-viśeṣātmā prema-suryāḿśu-sāmyabhāk
rucibhiś citta-māsṛṇya kṛd asau bhāva ucyate
The (love) specific state of the soul - atmā viśeṣa
in pure virtue - śuddha-sattva
as the rays of spiritual love manifest - prema-surya aḿśu sāmyabhāk
and consciousness is melted by the tastes (of love) - citta rucibhiś māsṛṇya
is called the beginning of spiritual love - kṛd asau bhāva ucyate.
This bhava is not the result of sadhana bhakti (practice of devotion).
In the continuous performance of
- Śravan (hearing about the pastimes of the Transcendental Lord),
- kirtan (praising the names, forms, qualities, and His plays) and
- other limbs of Saddhna-bhakti
one cultivates the desire
- to detach oneself from the world
- and to approach the deity of the heart.
When saddhana-bhakti has reached maturity,
it has removed all undesirable qualities and attractions from the heart of the sadhaka (practitioner).
At that time, by the mercy of the Lord or His devotee, bhava manifests in the soul of the sadhaka.
When these bhavas - buds of spiritual love -
1. melts the heart even more, much more than in the original stage of love,
2. it extraordinarily increases the feelings of transcendental ecstasy,
3. and gives a deep sense of mamata (ownership) in relation to Krishna,
then it is called prema - pure divine love - by the transcendental scholars .
This is how prema is described by Srila Rupa Gosvami in Bhakti Rasamrita Sindhu (1.4.1):
samyaṇ masṛṇita-svānto / mamatvatiśayaṇkitaḥ
bhāvaḥ sa eva sāndrātmā / budhaiḥ premā nigadyate
The state (when) one's own (love) nature continues to melt ("the heart") - samyaṇ sva anta masṛṇita
the desire to possess (Krishna) marks one - atiśaya mamatva aṇkitaḥ
and bhava becomes much stronger in the soul - bhāvaḥ sa eva atmā
is called Prema by the intelligent. - budhaiḥ premā nigadyate