My mother has been suicidal a couple of times during my life and I have a strange respect for it, for that complete refusal of life. On the other hand my mother's behaviour has caused me a lot of pain and I think has effected my psyche in negative ways. For one thing, if I come home and the house seems empty, I always walk around the house, check all the rooms, even in the basement, to see that my mother isn't lying there somewhere, dead.
I've been clinically depressed as well, and I agree with other posts that you lose your rational thinking and your personality is distorted by the drowning in sadness that is depression. At the time I was living alone and late one night everything felt so utterly hopeless (I can't remember if something had happened or if it was just the general state of things that made me want to die), I was crying violently and just put on my jacket and started walking into town. I decided that I was going to jump from an old crane in the north harbour district, and walked over the bridge in the cold and the snow. Eventually I stopped crying but just soldiered on, feeling like I had to make a desicion, everything or nothing, typically depressive thinking. I didn't feel anything, wasn't at all bothered by the cold, just kept telling myself not to chicken out. Anyway, when I got to the crane there was a big pile of snow covering the ladder which was surrounded by a sort of metal cage, and there was no way I could get up there, so I just turned around. I went home and slept and the next morning I cycled to school like nothing had happened, but I felt very cold and detached, in a joyful way, it was almost omnipotence. I could get out.
But afterwards, I got medication which made me better (therapy sadly didn't help me at all, but I'm still very sceptical about CBT and SSRI, and positive towards more advanced therapy). I never think about suicide for too long nowadays since it would cause great harm to my family.
Sorry for taking up so much space with this, and sorry if my english is a bit odd, I'm swedish and don't write in english very often.