I think it's a whole mixture of things for me now. It definitely was sadness when I first experienced ideation but that was decades ago. I'm not deeply upset or terribly angry now. It's a lot more placid than that! I feel like- after 43 years, I know myself. I know what I enjoy in life and what I don't. I simply don't think life is worth it! Perhaps it's closest to apathy but it isn't really that either because I do still enjoy some things. I just don't enjoy the majority of them!
One of those documentaries on suicide called 'Death Leap' had a psychiatrist in it who said he thought most people who committed suicide were angry. I think there is often anger there. Resentment at the very least. I guess I do have anger to some extent. Just at how the world is I suppose. But then- I guess- knowing we can't change it and we don't necessarily want to adapt to fit in it- maybe that's what makes us sad.
I think- by my sort of age though- it's a whole mixture of emotions- sadness, loneliness, cynicism, pessimism, apathy, anger, resentment, rebellion, grief, fear. The more variation you get that all point in the same direction- the more you become convinced it's the right choice for you.