No 1st hand experience, but 2nd hand.
I had a friend try to kill herself, I knew she wasnt OK and I tried my best to be there for her, but one day I found out (when an ambulance crew came looking for her in our building after a tip-off) that she had taken an overdose. I called her, and she answered, but I just couldn't convince her to want to live, she was ODing whilst i was on the phone with her, and I failed. Anyway, point is, she was convinced she wanted to die, but as luck would have it, she was found unconscious JUST in time, and since they knew what she took they managed to save her. Afterwards she just didnt want to talk about it and I respected that. As years went by we didn't really keep in touch, but i looked her up not too long ago. She is now married with kids.
You never know whats coming, she was CERTAIN that she was better off dead, and now she has a family and seems happy, that kind of thing is one of the main reasons I ruled out suicide as an option long ago.