I was always curious and hungry for knowledge as a kid, but what I lacked was the knowledge of where I can find more knowledge (the libraries in my childhood were crap; the most complex computer book was how to use Office). It wasn't until university that I realized how to research things and find the best resources to learn that I truly was able to teach myself. That happened at the end of my 3rd year of university, and my 4th year was spent barely attending class and instead teaching myself the required material on my own time, while I was also learning about things not taught in class.
edit: Argh, clicked submit too soon. added second paragraph.