Can you think of one life changing mistake you've made?

Some of us have emerged from the most painful circumstances with strong insights about who we are and what we want. Our sometimes stumbling attempts at growth and progress are necessary. We learned, we progressed. We went through exactly the experiences we needed to, to become who we are today. What painful lesson taught you the most and helped you grow to be the person you are today? Can you describe the one mistake that had the most impact on who you have become?