The jīva soul is struggling very hard on the tree of the material body, but as soon as he agrees to accept the other bird as the supreme spiritual master—as Arjuna agreed to do by voluntary surrender unto Kṛṣṇa for instruction—the subordinate bird immediately becomes free from all lamentations. Both the Muṇḍaka Upaniṣad (3.1.2) and Śvetāśvatara Upaniṣad (4.7) confirm this:
samāne vṛkṣe puruṣo nimagno
'nīśayā śocati muhyamānaḥ
juṣṭaṁ yadā paśyaty anyam īśam
asya mahimānam iti vīta-śokaḥ
"Although the two birds are in the same tree, the eating bird is fully engrossed with anxiety and moroseness as the enjoyer of the fruits of the tree. But if in some way or other he turns his face to his friend who is the Lord and knows His glories—at once the suffering bird becomes free from all anxieties." Arjuna has now turned his face towards his eternal friend, Kṛṣṇa, and is understanding the Bhagavad-gītā from Him. And thus, hearing from Kṛṣṇa, he can understand the supreme glories of the Lord and be free from lamentation.
Arjuna is advised herewith by the Lord not to lament for the bodily change of his old grandfather and his teacher. He should rather be happy to kill their bodies in the righteous fight so that they may be cleansed at once of all reactions from various bodily activities. One who lays down his life on the sacrificial altar, or in the proper battlefield, is at once cleansed of bodily reactions and promoted to a higher status of life. So there was no cause for Arjuna's lamentation.
(Bhagavad-Gita--2:22-purport).

There are different varieties of living entities, 8,400,000 varieties. How many you have seen? Therefore you have to take knowledge from the perfect source. Then we you can understand. Tad-vijñānārthaṁ gurum eva abhigacchet. This is Vedic injunction. If you want to know perfectly everything, then you must go to the proper teacher. Then you will learn. But how you can imagine from here? A dwarf is trying to touch the moon. How it is possible? That is not possible. The Vedic injunction is in order to... Tad-vijñānārtham. Higher science. Vijñāna means science. If you want to know higher science—not this science, simply filling of the belly, not this science—higher science, which is above fulfilling the belly, that, for that purpose, you have to go to guru. Guru means who knows more than you. That is guru. So who can know more than Kṛṣṇa? Therefore we have to accept Kṛṣṇa as guru and learn from Him. Then you'll get perfect knowledge.
(Lecture on Srimad Bhagavatam--6:1:22--Honolulu--22nd. May, 1976).

The camel is a kind of animal that takes pleasure in eating thorns. A person who wants to enjoy family life or the worldly life of so-called enjoyment is compared to the camel. Materialistic life is full of thorns, and so one should live only by the prescribed method of Vedic regulations just to make the best use of a bad bargain. Life in the material world is maintained by sucking one's own blood. The central point of attraction for material enjoyment is sex life. To enjoy sex life is to suck one's own blood, and there is not much more to be explained in this connection. The camel also sucks its own blood while chewing thorny twigs. The thorns the camel eats cut the tongue of the camel, and so blood begins to flow within the camel's mouth. The thorns, mixed with fresh blood, create a taste for the foolish camel, and so he enjoys the thorn-eating business with false pleasure. Similarly, the great business magnates, industrialists who work very hard to earn money by different ways and questionable means, eat the thorny results of their actions mixed with their own blood. Therefore the Bhāgavatam has situated these diseased fellows along with the camels.
(Srimad Bhagavatam-2:3:19-purport).