Yes, I've always known I'll die by my own hand. I have to say, I've never attempted (well.. ish, once after my beloved grandpa died at the age of 7, so how serious was that, really?). But I've known since I was quite young that eventually I will kill myself. I want to be able to make my own end of life decision, I don't want to grow infirm, I don't plan on fighting any debilitating disease or see myself waste away. That was always the idea, I will die, when I feel I am ready to die, when I'm incapable to take care of myself and become a burden to others to take care of.
I have watched my grandparents die slowly over a prolonged period of time, from cancer, from old age, distorted and not looking like the people I knew, mentally and physically completely broken. I promised myself I wouldn't go through that. They also asked, in the end, to please be allowed to die, but since that is not allowed in my country, they got 'the best care possible' and received some more time on this beautiful planet, lying on intensive care with closed curtains, unable to eat themselves, unable to go to the bathroom or even speak. So for me, dying because my body can't go any further, that was always an acceptable option.
I recently needed to, and still am, making peace with death due to not being able and not being willing to go on for mental reasons. This is tougher than the physical conditions, seeing as the real question is when your mind is truly broken. Human minds can take more then human brains think, usually when you think 'It can't get any worse, I cannot go on anymore'.. you still can. But I've made my decision, basically I committed to it and I don't question it anymore. The peace with it is there, the question is just the timing now.