Are we talking about the very best 'feel good' factor here, in which case I could relate one or two but at the very top of the list would be the night I attended a RTA involving three people known to me personally, two of whom were pilots, and one of whom and his passenger didn't survive.The other was removed from the wreck and transported to the nearest hospital. An hour or two later and still in the early hours , I was out running and the OC of that squadron pulled up alongside and 'invited' me to join him to visit the hospital. It appeared they needed my relatively rare blood for a donation to the chap I had helped remove.He survived, and some six months later I wandered into the Mess and he spotted me and came over: "I believe I owe you a pint" he said! He later returned to University and qualified as a Doctor, and specialised in aviation medicine for many years. Feel good? You betcha! This happened to me twice by the way, and somewher in Oz there is a soldier who doesn't know how lucky he was that I was the only B.Neg donor within hundreds of miles.