I don't know…the media image is someone who is "mentally ill," or "did it on the spur of the moment," and all that shit. And I don't believe a bit of it.
I think the vast majority of people who commit suicide have been thinking about it for a long fucking time. They've been torturing themselves with the question "Why the fuck haven't I killed myself already?" for years.
Then, eventually, apathy begins to set in. As the suicide ideation increases, and the years slip by, they care less and less about the world, and by extension, themselves. Until, slowly but surely, suicide becomes a mere afterthought and is something they can do with ease.