My biggest mistake was while studying in university in 2004-05, i took three electives in AI, such as Neural Networks and Machine Learning. Even though I enjoyed the subjects and did well in them, I was too afraid to major in them and make a career out of it. I got scared by the math but also life took over and i probably didn't see myself having a career in AI. Now 15 years later looking back, it seems such a dumb mistake not pursuing those further.