Recently I have come across many accounts of people who are seemingly ok with death.

As examples:

Cato committing suicide in front of Caesar, living thanks to a surgeon and then subsequently tearing off his bandages and ripping his own insides up to finish the job.

The Tezcatlipoca representative in Aztec culture. A youth would volunteer to play a part in a religious festival where he would spend a month dressed up as the aforementioned god and be given a harem of beautiful women, before proceeding through the streets playing a flute, to a temple where he would be sacrificed.

I could go on and give more examples of things like this in ancient history (Spartan and Samurai culture spring to mind, not to mention Child sacrifice in pre-Colombian culture. How would a mother/father justify this to herself?)

Anyway, my curiosity lies in the mindset not of these cultures but of the person who is choosing to die. How did these people see death? Would they not have been afraid of the physical pain they would experience as they willingly walked towards their death? How on earth did they override the basic instinct to fight death?

To me choosing death for honor or religion unimaginable as a course of action, but I know I am a product of my environment. I am interested in the environment that creates this mindset.

The main question is: How would I as a human sacrifice/honor suicide feel about my death?

As follow ups: what changed so that we in the modern world (Certain states and groups excluded) hold life in such high regard and do our best to maintain our own lives and avoid death? When did this change occur and how?

PS. I really hope this question is not seen as being to general, so I have tried to limit my questions to a few historic examples I am aware of.