Out on Top
People can be great at what they do. When you see someone being great at what they do, though, you don't really question it. There's no real sense of urgency -- it's just someone doing something really well. It's not til later, when they're done and will never be doing that thing again, do you realize how truely great they were. How legendary they could end up being. The best way to be remembered as a true legend is to go out while on top. There's a time when you realize that you might not be able to do something for much longer, so you put all your energy into making your final appearance your greatest one yet.
Chuck Norris, for instance, won six consecutive middleweight Karate world championships from 1968 to 1974. He knew that he could only carry on such a title for so long before his old age got the best of him. He retired in 1974 undefeated. Now he is a legend.
Another example... 90s Swedish punk band, Refused. Refused were great at what they did, which was play highly energetic and chaotic hardcore punk. However, interband squabbling was getting the best of them. Musically, they clicked perfectly, but the problem is that when you have too many talented people organized doing the same thing, social or ego problems may arise. People knew they were great at what they did and even thought that their 1998 release of "The Shape of Punk to Come: A Chimerical Bombination in 12 Parts" was terrific. Refused did not become legendary, however, until they broke up while on tour just months after that album was released. Since then, that album has gone from great album to classic album. Refused are now legends.
Finally, the person that I think is the ultimate example of this... Michael Jordan. Michael Jordan, even before he was retired, was recieving labels from some as "the greatest baskeball player ever". He really was great. An hero, even. When he announced that he would retire after the 1998 pro season, many people were saddened by this news. Yeah, sure he was getting a little older than the other players, but he still had that raw talent working for him. Jordan knew better than anyone else that basketball -- as a profession -- was wearing him out and that he wouldn't be as amazing as he was forever. When the Bulls made it to the finals that year, Jordan scroed the game winning -- and championship winning -- shot. Now, Michael Jordan is a legend. Ignore the fact that he kept coming back to the game, that was just out of passion for it, just like how Paul McCartney keeps releasing records.