The idea of sacrificing oneself to achieve something greater is regarded as heroic. We have all grown up seeing Hollywood movies where the hero takes enormous risks to reach his goals, and the outcome is always the same, the hero wins and he never gets hurt, not seriously anyway. Think of Indiana Jones and James Bond, for instance.
But let’s get back to the real life. We humans are social animals and throughout the history of mankind we have had two main tasks to ensure our existence, getting food and keeping our tribe safe from danger. Throughout the history we have become very good at this and actually it is the main reason why we humans still exist today.