I know exactly what you mean about the calmness...I've always been terribly afraid of dying but I know I'm ready now because I have no fear about it.
As for method, I've given a lot of thought to the options. I've considered several methods and done some comparative research on things like success rates; required preparations; time required for fatality; likelihood of interruption; reversibility; danger to others; level of pain/discomfort; and other factors.
For me I don't think hanging is an option because the failure rate is so high and it's so easy to get it wrong; jumping is also out because I suffer from acrophobia and I know I'll never have the courage to take the leap; ingested poisons like N are not good options because I have always had a low threshold to nausea and vomiting; intravenous poisons are not a viable option for me because I have an aversion to needles and I wouldn't be confident of acquiring the right substance or finding the right vein; guns are not widely available here and having seen photos of several people who survived failed attempts definitely put me off; trains seem a relatively quick and certain method but the violence and disfigurement really put me off as well - the real videos of people dying this way are gruesome. Going in front of a car traveling at high speeds is something you can find videos for easily too but again they are violent and gruesome, not to mention enormously dangerous to the innocent driver. I honestly don't think I'd have the guts to touch something with enough electricity to be certain of fatality (never mind that all of the electrocution videos I've seen result in gruesome remains); burning and drowning have always terrified me so I don't think I could actively pursue either of those means of exit.
From all I've read and from my own predispositions, I feel like inhaled poisons are the best option. My first plan was to generate Hydrogen Sulfide Gas in a confined space. This method offered several advantages: firstly, it's relatively easy to come by the necessary materials in a hardware store and it's toxicity is extremely high (as high as hydrogen cyanide gas but far easier to acquire) with death occurring in minutes. The process is painless and offers no real discomfort because, although the mixture reportedly smells of rotten eggs, the gas paralyses the olfactory sense almost immediately, unconsciousness quickly follows and within minutes it will have paralysed the respiratory system resulting in death by cellular hypoxia. It is reported that death occurs so rapidly that the remains always appear to be in a peaceful slumber. This method for me offered everything I could want: it would be relatively simple to produce the agent; the effect would be rapid and free of discomfort; death would be non-violent, non-disfiguring and irreversible.
I subsequently discovered that a different method offered all of these qualities plus the possibility of appearing like an accident. For the sake of some of the people I will leave behind, this possibility has a particular value. Despite work-place fatalities resulting from hydrogen sulfide poisoning being not uncommon for agricultural, sewerage and sanitation workers; there's no way a bucket of bath-salts and garden fungicide in the back of my car could appear as anything but a deliberate suicide by hydrogen sulfide (aka 'detergent suicide'). Ultimately, Carbon Monoxide is the method I have settled on because it's almost as lethal a gas as hydrogen sulfide, offers the same level of toxicity and rapidity of effect; but it is even easier to produce and results in large numbers of accidental deaths every year.
For me the bottom line is to find a way out that is certain and peaceful. I think this is it.
