If I believed that my wife and or kids were in imminent danger and that I would risk my life to successfully save them, I would do so. Most of us would do the same for a stranger. The you/I distinction dissolves in such emergencies. We would all deliberately die in certain critical situations. (this may not apply to social psychopaths devoid of conscience, or people incapable of a physical response.)

Unknowingly we risk our life in situations in which power dynamics are arrainged against us in ways in which we are totally unaware, be it an aggresive driver's motives or an intelligence officer's misplaced or deranged agenda.Everyday we may accidently die because of a trusting belief that society and individuals would do the right thing. some don't.

Meaningful or unknowing sacrifice is something each of us do each day that carries the consequence ofn possibly dieing.

Questions of martyrdom and out right self sacrifice are an entirely seperate issue in my way of thinking. Those actions are the result of training ie. religious, military or political, and are not innate to human/primate nature.