In this quote from Great Expectations, Pip is referring to the day he first became acquainted with Miss Havisham and Estella. Before this day, he had no idea what it was like outside of his life in his average home. When he saw the way of life in the Manor House his view of the world changed completely. He realized that he could have a better life than the path he was headed for as a blacksmith. He made the decision to make the most of his life and get educated so he could become more than what was expected of him.
A day in my own life that began my "chain" was the day I realized I couldn't go without ballet. I was in sixth grade, and I had just taken a year off of dancing to focus on basketball. When the decision came to choose a priority for the coming year, I recognized that I enjoyed dancing more than playing basketball. After that day, I was more focused than ever on improving my technique in ballet. Although I kept playing basketball, I knew dancing was the higher priority and that decision put me on the path that I am now on.