As Eliot Spitzer is resigning as New York Governor, I went searching for his golden rule quote from an old Business 2.0 magazine. Given his background as attorney general I always found it cynical, but for unethical persons it will always be sound advice:
"Never write when you can talk. Never talk when you can nod. And never put anything in an e-mail."
However, I also found another quote that is also useful to ethical persons. Especially when times are good.
"Don't confuse luck with skill when judging others, and especially when judging yourself." - Carl Icahn, investor.
(It should, however, be combined with the classic quote attributed to golfer Gary Player: "The harder you work, the luckier you get.")
Even for people with great skills luck plays a huge role in how their lives are shaped. (Industry example: Being or not being at Google probably had a far larger impact on how well an Internet professional did financially between 2000 and 2007 than how skilled she or he was.)
Choices that seem obvious in hindsight, rarely are when they are made. But I don't believe outcomes are random, hence the role of Gary Player's quote.