In plain words
You must develop a temper of mind that neither sinks nor swells. This is the very discipline of a true devotee. What do you think Bhakti is? It is not doing pūjās and vratas. You must not take back the Prema you have poured out on God. That alone is true Bhakti.
Lakṣmaṇa's Śaraṇāgati
Lakṣmaṇa set out for the forest with Sītā and Rāma. The three of them reached the Citrakūṭa hill. Rāma looked at the place: “Lakṣmaṇa! We have come to a very peaceful spot. Sītā, who has never known the heat of the sun, is very tired. So build a leaf hut here for us to live in,” he said. “Where shall I build it, brother?” asked Lakṣmaṇa. Rāma said, “Build it wherever you like.” Rāma's words hurt Lakṣmaṇa deeply. “Ah, what a sin I must have committed, to have to hear such harsh words!” he lamented. Then Mother Sītā: “Lakṣmaṇa! Your brother has not scolded you or struck you, has he! Why are you grieving so much?” she asked. Lakṣmaṇa: “Mother! Were Rāma to scold me or strike me, I would only be glad. But he has said that I have a wish of my own, apart. That word pained my heart as if it had been stabbed with knives. Rāma's wish itself is my wish, is it not! What sin have I committed, that he tells me to build it wherever I please?” he said. Then Rāma showed Lakṣmaṇa a spot and said, “My dear, build it there.”
What is Śaraṇāgati? Your will and God's will must be one and the same. Whatever happens, you must take it as God's will itself. You must not give the least room to the debate, ‘This is good, this is bad, this is hardship, this is happiness.’ Whatever God tells you to do, that you must do! You must not question, ‘Why? What for?’ That alone is the mark of a true devotee. Whatever God does is only for your good! He put the Pāṇḍavas through many hardships. But it was through those very hardships that their fame spread through the world. With unshaken Bhakti they bowed to God's command and in the very end won victory. With Bhakti and prapatti you can achieve any task in the world.