Whether true or not, I'm not sure, but this story was told to me recently and I think more appropriately defines heroism than anything else I have heard.
A little girl was hospitalized for some life threatening problem. She was in need of blood and for some reason the only donor who would work was her 9 year old brother. It was explained to him that his sister needed his blood and after thinking it over for a bit, he agreed to the donation.
The staff prepped him and did their best to make him as comfortable as possible. He maintained a determined look thoughout the blood draw but seemed unable to keep a tear out his eye.
After the hospital staff was finished, the Doctor spoke with him briefly and explained how he might have saved his sisters life. He was told he should be very proud of what he had just done. The little boy had a look of fear in his eye, and the Doctor did his best to assure him that he was fine, and his sister would be too. Still not able to cheer the boy up, the Doctor asked him what was wrong. The boy explained nothing was wrong and he was glad to help his sister, but he did want to know, that since his blood had been taken...
...how long would it be until he died.
Never be afraid to make a difference