Not understanding human nature can truly lead to a lifetime of mistakes. When you're young, you might not understand this saying, but by the time you do, it's already too late. I only realized this truth after I turned 30. When I was in my twenties, working in sales at Alipay Koubei, I visited dozens of merchants every day, working tirelessly to close deals. My colleagues told me I needed to maintain good relationships with customers, but I didn't take it seriously, thinking, "Just do your job well."