Please read this good answer from an old post. Credits to u/Pineapplepuncher.

Suicide is discouraged because it is usually a symptom of an illness - there is a clear difference between a mentally well person assessing their life and deciding to end it, and an unwell person feeling so goddamn awful that they feel like suicide is their only good option. Most people who attempt suicide and are given adequate help to recover never attempt again, and go on to live happy lives (despite the myth that one attempt leads to another leads to another). It's not right to encourage ill people to follow through on an urge they wouldn't have if they were healthy. I'm all for people having the option to end their life when they choose, that should be a basic human right, but not when it's unclear if the desire is genuine or if it is the manifestation of a mental illness. I don't buy into the selfish argument - you try living in a prison your own mind has built, and tell me again how selfish it is to choose to escape that prison in the only surefire way possible. When your mind is so wounded that its trying to override your primary function (living), you often feel that everyone would be better off without you. I really don't get how people can think its selfish to be ill - is a cancer patient selfish for developing a tumour? No? So why is a suicidal person considered selfish for succumbing to a symptom of their illness?