What should i say to suicidal people?

So I just watched 13 reasons why. I can't sleep, btw haha. I've been searching online the whole night looking up things about suicide, asking why they do it? I've been through shit myself and I've met people who have gone through worse shit than me but I don't get why people commit suicide. I'm not judging or anything, I just wanna know and try to understand and possibly help. I finally came across this post, its someone who's suicidal but it's not because they've lost someone or anything. They just don't wanna be here.

These are some of things he or she said "It's not that my life is terrible or that I've lost someone that I care about, I just truly don't want to be here. I do not want to be a part of society and I feel it's unfair that I've been thrown into this life and am expected to live it just because I was born." "Why am I the selfish one for wanting to leave this god forsaken planet? Aren't they selfish for wanting to keep me here even though I'm miserable?" "I don't think it's a mindset or a mood. It's my personality. I hate life.. I hate society..." "...every time I tell someone any of this, they act like I'm crazy for not loving life with a burning passion..." If you wanna the read the whole thing, here's the site: https://www.google.com/amp/s/amp.reddit.com/r/SuicideWatch/comments/2rm9fe/i_dont_understand_why_suicide_is_so_frowned_upon/

My question is...how can I help someone who's like this? I wanna help if I ever come across someone like this. I probably cant change their mind or do much to help them really, but is there any way I can say to them that might help them feel better even just a little bit? A suicidal person spoke at TED Talk saying that you can't really change someone's mind from committing suicide, but I still want to try. I'm asking these questions because I want to be prepared just in case. Thanks.