Imho, there are a lot of different aspects to this and it can be different reasons for different people.
Also, none of us here has successfully committed suicide... so none of us here have really conquered this and can therefore truly speak as "authorities".
Here is an excerpt of Alberto Radicati's 1732 work, A Philosophical Dissertation upon Death: Composed for the Consolation of the Unhappy (a book that was not only banned, but caused both Radicati and his translator to be jailed — because it basically says anyone can commit suicide, FOR ANY REASON THEY DAMN WELL WANT even just being "unhappy", and it is NO PROBLEM WHATSOEVER TO DO SO = that any difficulties you have committing suicide are based on abject lies you're allowing yourself to believe) that makes some good points...
The whole book is available on Amazon Kindle for $0.99 USD.
"Whence then does proceed this Dread? It proceeds from the Knowledge of a Danger: And this Danger is known either through some actual Experience, or else it is known without any such Experience, but merely from a Credit reposed in some one who tells a plausible story of such or such Things being dangerous. Of these the First is real: The Second may be fallacious. However, neither the one nor the other Knowledge is innate, or born with us, but contracted long after our being born.
...
This Credence established in Human Minds, Men feared to die; not merely through a Dread or Reluctance to cease from being in Life, but for Fear of encountering new and more grievous Evils than any they had known or suffered while they were living. And what I here say is confirmed to us by Experience; since we see that little Children, such as have not as yet been capable of receiving from their Mothers, etc. any Manner of Idea of the Pains and Punishments of the other Life, do die without the least Fear or Apprehension; neither do they undergo any Pain or Torment but what proceeds from the Disease which consumes them: But they have not their Spirits on the Rack with the horrible Contemplations of Infernal Flames, because they have not thereof any Knowledge: Contemplations! which render Death most dreadful to Men, and which cause them to suffer a Thousand racking Tortures, none of which they would undergo, were not their Minds clouded with the false Idea of a Danger which exists not. Let us then remove away this vain Fear from Human Intellects, and we shall see Men will quit Life willingly: The which is exemplified in those who die Martyrs, who with abundance of Pleasure endure the greatest and most cruel tortures, and most ardently desire to lose their Lives on that Occasion, because they firmly believe they shall not meet with that menaced Danger, since they cease to live purely for the Sake of the Defence of their Religion.
The false Ideas which we acquire through the evil Instructions which we receive from those who are entrusted with our first Education, are what cause in us this Fear of Death. The bad Principles which we suck in with our Milk are what, taking fast Root within us, do adulterate our Minds and corrupt our Imaginations. Let us then purify our Intellectuals, making Reflections on the Falsity of those Principles, which derive their Origin only from the Malice and Impostures of Men. Let us pass a strict Examination on all Beliefs, and we shall know, that they are all the Offsprings of Human Wit and Policy; since they all have the very same Characters, and all the self-same Foundation, as I have clearly demonstrated in another of my Performances [In my Historical and Political Discourses, Dis. XI]; and then we shall not fear Death. We shall not fear it, I say; because we shall then comprehend Death to be what delivers us from the Persecutions of our Adversaries, from the Tyranny of the Mighty, from the Disquiets which molest us, from the Anxieties which cruelly torment us, from the Infirmities which tyrannize over us, and, in a Word, from all Misery. Finally, it is Death alone which frees us from the slavish Bondage of Men, rendering us all Equals, such as Nature created us when she gave us our Existence. To fear Death then is an Error: A truly great Error! Since the Infant, the Idiot, the Mad, the Superannuated, and the Maintainer of some fond Religious Chimera fear it not, notwithstanding they are devoid of Reason; why then should it be feared by a Rational Man, having a Capacity of judging Reason, and of conceiving the Truths here exhibited?"
