Of all the sports I follow and have participated in.. one that comes to mind is baseball. The best hitters in the world have a success rate of around a .300 avg. Thinking of the mental game , hitting mechanics, length of season, injuries etc. The mind games it plays of you after going 0-10 is crazy. Not to mention the guy you have to hit off of can pitch on avg around 95mph with movement, change speeds, make the ball spin, etc.... That's the one that comes to the top of my head when we are talking about how difficult it is to be successful at least.