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7. "Not buying Amazon stock in the '90s"
— Anne, an administrative assistant from Renning, Pennsylvania

Money regret: "I wasn't savvy enough. In your 40s when you're working to survive, you don't have the extra money to buy stock. Now that I'm older and the kids are grown, you have the opportunity and you know what brokers do."

Essential lesson: "Ask for advice, as odd as it is, about things you don't know. Don't be embarrassed. Just go ask somebody. Every company, or every major corporation, they've got people. Go to people you're associated with in the company you work for, and if that's not available, go to your parents. Ask who your parents used. I didn't have the sense to do that and I should have."