What investing lesson took you the longest to learn?

Summary

• The post asks community members to share the investing lesson that took them longest to internalize, focusing on behavioral wisdom rather than specific stock picks.
• The author’s implicit thesis is that deep, often counterintuitive behavioral lessons (patience, cutting losses, avoiding sunk-cost attachment) are more valuable than any single trade.
• Quality assessment: This is speculative/reflective noise, not a DD. No financial data, no company analysis, no actionable thesis.