One who is in the renounced order of life should not be allured by the glamor of the householder's worldly possessions and thus become subservient to worldly men. For one who is in the renounced order of life, this is much more dangerous than drinking poison and committing suicide.
(Srimad Bhagavatam---1:4:8---purport).

For a transcendentalist, therefore, who at all wants to be promoted to the kingdom beyond material miseries, it is worse than suicide to deliberately indulge in sex life, especially in the renounced order of life. Sex life in the renounced order of life is the most perverted form of religious life, and such a misguided person can only be saved if, by chance, he meets a pure devotee.
(Srimad Bhagavatam---2:6:20---purport).

Material life means eat, drink, be merry and enjoy, with no concern for understanding one's spiritual identity and the process of spiritual advancement. Since materialistic people are concerned with the tongue, belly and genitals, if anyone wants to advance in spiritual life he must be very careful about associating with such people. To associate with such materialistic men is to commit purposeful suicide in the human form of life. It is said, therefore, that an intelligent man should give up such undesirable association and should always mix with saintly persons.
(Srimad Bhagavatam---3:31:32---purport).

One of His associates, Junior Haridāsa, committed a great mistake by lustfully glancing at a young woman. The Lord as Supersoul could detect this lust in the mind of Junior Haridāsa, who was at once banished from the Lord's association and was never accepted again, even though the Lord was implored to excuse Haridāsa for the mistake. Junior Haridāsa afterwards committed suicide due to being disassociated from the company of the Lord, and the news of suicide was duly related to the Lord. Even at that time the Lord was not forgetful of the offense, and He said that Haridāsa had rightly met with the proper punishment.
(Srimad Bhagavatam--summary).

One who is constantly thinking of activities to earn money and gratify the senses is following a path which is suicidal. Factually all human society is following this path. Some way or other, people are determined to earn money or get money by begging, borrowing or stealing and applying that for sense gratification. Such a civilization is the greatest obstacle in the path of self-realization.
(Srimad Bhagavatam---4:22:33---purport).

A confused, frustrated man cannot get relief by committing suicide because suicide will simply lead him to take birth in the lower species of life or to remain a ghost, unable to attain a gross material body. Therefore the perfect course is to retire altogether from sinful activities and take up Kṛṣṇa consciousness. In this way one can become completely perfect and go back home, back to Godhead.
(Srimad Bhagavatam---4:26:10---purport).

When Sanātana Gosvāmī came to Jagannātha Purī, he stayed under the care of Haridāsa Ṭhākura for some time, and Śrī Caitanya Mahāprabhu was very happy to see him. The Lord informed Sanātana Gosvāmī about the death of his younger brother, Anupama, who had great faith in the lotus feet of Lord Rāmacandra. One day Śrī Caitanya Mahāprabhu said to Sanātana Gosvāmī, "Your decision to commit suicide is the result of the mode of ignorance. One cannot get love of God simply by committing suicide. You have already dedicated your life and body to My service; therefore your body does not belong to you, nor do you have any right to commit suicide. I have to execute many devotional services through your body. I want you to preach the cult of devotional service and go to Vṛndāvana to excavate the lost holy places." After having thus spoken, Śrī Caitanya Mahāprabhu left, and Haridāsa Ṭhākura and Sanātana Gosvāmī had many talks about this subject.
(Sri Caitanya Caritamrta---3:4----summary).

"Acts such as suicide are influenced by the mode of ignorance, and in ignorance and passion one cannot understand who Kṛṣṇa is."
(Sri Caitanya Caritamrta---3:4:57---translation).

"Measures like suicide are causes for sin. A devotee never achieves shelter at Kṛṣṇa's lotus feet by such actions."
(Sri Caitanya Caritamrta----3:4:60---translation).