The conditions of each and every planet are different, and different classes of human beings are accommodated there for particular purposes mentioned in the codes of the Lord. But, puffed up by tiny success in material advancement, sometimes the godless materialists challenge the existence of God. Rāvaṇa was one of them, and he wanted to deport ordinary men to the planet of Indra (heaven) by material means without consideration of the necessary qualifications. He wanted a staircase to be built up directly reaching the heavenly planet so that people might not be required to undergo the routine of pious work necessary to enter that planet. He also wanted to perform other acts against the established rule of the Lord. He even challenged the authority of Śrī Rāma, the Personality of Godhead, and kidnapped His wife, Sītā. Of course Lord Rāma came to chastise this atheist, answering the prayer and desire of the demigods. He therefore took up the challenge of Rāvaṇa, and the complete activity is the subject matter of the Rāmāyaṇa.
(Srimad Bhagavatam----1:3:22----purport).

The Lord is specifically the protector of the cows and the brāhmaṇas, and hence He enhances the prosperity of the world. He rewarded the administrative demigods by effective weapons to conquer the demons through the agency of Viśvāmitra. He was present in the bow sacrifice of King Janaka, and by breaking the invincible bow of Śiva, He marriedSītādevī, daughter of Mahārāja Janaka.
(Srimad Bhagavatam----1:12:19----purport).

After His marriage He accepted exile in the forest for fourteen years by the order of His father, Mahārāja Daśaratha. To help the administration of the demigods, He killed fourteen thousand demons, and by the intrigues of the demons, His wife, Sītādevī, was kidnapped by Rāvaṇa. He made friendship with Sugrīva, who was helped by the Lord to kill Vali, brother of Sugrīva. By the help of Lord Rāma, Sugrīva became the king of the Vāṇaras (a race of gorillas). The Lord built a floating bridge of stones on the Indian Ocean and reached Laṅkā, the kingdom of Rāvaṇa, who had kidnapped Sītā. Later on Rāvaṇa was killed by Him, and Rāvaṇa's brother Vibhīṣaṇa was installed on the throne of Laṅkā.
(Srimad Bhagavatam----1:12:19----purport).

Lord Rāmacandra was ordered by His father, Mahārāja Daśaratha, to leave home for the forest under awkward circumstances, and the Lord, as the ideal son of His father, carried out the order, even on the occasion of His being declared the King of Ayodhyā. One of His younger brothers, Lakṣmaṇajī, desired to go with Him, and so also His eternal wife, Sītājī, desired to go with Him. The Lord agreed to both of them, and all together they entered the Daṇḍakāraṇya Forest, to live there for fourteen years. During their stay in the forest, there was some quarrel between Rāmacandra and Rāvaṇa, and the latter kidnapped the Lord's wife, Sītā. The quarrel ended in the vanquishing of the greatly powerful Rāvaṇa, along with all his kingdom and family.
(Srimad Bhagavatam----2:27:23----purport).

It is understood that once Hanumān, the great devotee of Lord Rāmacandra, said that he knew that Nārāyaṇa, the husband of Lakṣmī, and Rāma, the husband ofSītā, are one and the same, and that there is no difference between Lakṣmī and Sītā, but as for himself, he liked the form of Lord Rāma. In a similar way, some devotees worship the original form of Kṛṣṇa. When we say "Kṛṣṇa" we refer to all forms of the Lord—not only Kṛṣṇa, but Rāma, Nṛsiṁha, Varāha, Nārāyaṇa, etc. The varieties of transcendental forms exist simultaneously.
(Srimad Bhagavatam----2:24:31----purport).

Although Rāvaṇa tried to abduct the goddess of fortune Sītādevī from the custody of Lord Rāmacandra, he could not possibly do so. The Sītādevī he forcibly took with him was not the original Sītādevī, but an expansion of māyā, or Durgādevī. As a result, instead of winning the favor of the real goddess of fortune, Rāvaṇa and his whole family were vanquished by the power of Durgādevī (sṛṣṭi-sthiti-pralaya-sādhana-śaktir ekā (Bs. 5.44)).
(Srimad Bhagavatam----5:18:22----purport).

The emotions a lover and beloved feel when separated from one another are actually very blissful, although apparently painful. Therefore the separation of Lord Rāmacandra from Sītādevī, as well as the consequent tribulation they suffered, is but another display of transcendental bliss. That is the opinion of Śrīla Viśvanātha Cakravartī Ṭhākura.
(Srimad Bhagavatam----5:19:5----purport).

The Lord delivered Sītādevī from the Aśoka forest and carried her in a flower airplane to His capital Ayodhyā, where He was received by His brother Bharata. When Lord Rāmacandra entered Ayodhyā, Bharata brought His wooden shoes, Vibhīṣaṇa and Sugrīva held a whisk and fan, Hanumān carried an umbrella, Śatrughna carried the Lord's bow and two quivers, and Sītādevī carried a waterpot containing water from holy places. Aṅgada carried a sword, and Jāmbavān (Ṛkṣarāja) carried a shield. After Lord Rāmacandra, accompanied by Lord Lakṣmaṇa and mother Sītādevī, met all His relatives, the great sage Vasiṣṭha enthroned Him as King. The chapter ends with a short description of Lord Rāmacandra's rule in Ayodhyā.
(Srimad Bhagavatam----9:10--summary).

The separation of Lord Rāmacandra from Sītā is spiritually understood as vipralambha, which is an activity of the hlādinī potency of the Supreme Personality of Godhead belonging to the śṛṅgāra-rasa, the mellow of conjugal love in the spiritual world. In the spiritual world the Supreme Personality of Godhead has all the dealings of love, displaying the symptoms called sāttvika, sañcārī, vilāpa, mūrcchā and unmāda. Thus when Lord Rāmacandra was separated from Sītā, all these spiritual symptoms were manifested.
(Srimad Bhagavatam----9:10:11----purport).

It was actually impossible for Rāvaṇa to take away Sītā. The form of Sītā taken by Rāvaṇa was an illusory representation of mother Sītā—maya-sītā. When Sītā was tested in the fire, this māyā-sītā was burnt, and the real Sītā came out of the fire.
(Srimad Bhagavatam----9:10:11----purport).

Not only was mother Sītā powerful, but any woman who follows in the footsteps of mother Sītā can also become similarly powerful. There are many instances of this in the history of Vedic literature. Whenever we find a description of ideal chaste women, mother Sītā is among them. Mandodarī, the wife of Rāvaṇa, was also very chaste. Similarly, Draupadī was one of five exalted chaste women. As a man must follow great personalities like Brahmā and Nārada, a woman must follow the path of such ideal women as Sītā, Mandodarī and Draupadī. By staying chaste and faithful to her husband, a woman enriches herself with supernatural power.
(Srimad Bhagavatam----9:10:27----purport).

It may be noted that these particular Deities of Rāma and Sītā have been worshiped from the time of King Ikṣvāku. Indeed, They were worshiped by the royal princes even before the appearance of Lord Rāmacandra. Later, during Lord Rāmacandra's presence, the Deities were worshiped by Lakṣmaṇa. It is said that just three months before his disappearance, Śrī Madhvācārya received these Deities and installed them in the Uḍupī temple. Since then the Deities have been worshiped by the Madhvācārya-sampradāya at that monastery. As far as the Śrī Vaiṣṇavas are concerned, beginning with Rāmānujācārya, they also worshiped Deities of Sītā-Rāma. Sītā-Rāma Deities are also being worshiped in Tirupati and other places. From the Śrī Rāmānuja-sampradāya there is another branch known as Rāmānandī or Rāmāt, and the followers of that branch also worship Deities of Sītā-Rāma very rigidly. The Rāmānuja-sampradāya Vaiṣṇavas prefer the worship of Lord Rāmacandra to that of Rādhā-Kṛṣṇa.
(Sri Caitanya Caritamrta----2:9:11----purport).

It is not that Rādhārāṇī is separate from Kṛṣṇa. Rādhārāṇī is also Kṛṣṇa, for there is no difference between the energy and the energetic. Without energy, there is no meaning to the energetic, and without the energetic, there is no energy. Similarly, without Rādhā there is no meaning to Kṛṣṇa, and without Kṛṣṇa, there is no meaning to Rādhā. Because of this, the Vaiṣṇava philosophy first of all pays obeisances to and worships the internal pleasure potency of the Supreme Lord. Thus the Lord and His potency are always referred to as Rādhā-Kṛṣṇa. Similarly, those who worship the name of Nārāyaṇa first of all utter the name of Lakṣmī, as Lakṣmī-Nārāyaṇa. Similarly, those who worship Lord Rāma first of all utter the name of Sītā. In any case—Sītā-Rāma, Rādhā-Kṛṣṇa, Lakṣmī-Nārāyaṇa—the potency always comes first.
(Teachings of Lord Caitanya).