At age 57, it's easier for me to point to books, and I think there's three main inflection points for me. When I was about 15 I read Philip K. Dick's "Confessions of a Crap Artist", which really opened my eyes to how we each live in our own subjective version of reality. At age 17, I read Ram Dass's "Be Here Now", which exposed me to eastern spiritual traditions (I'm an atheist, but this was still very eye opening and, with Dick, made me realize that religions can be interesting and valuable while also being full of bullshit). Much later in life, learning about Robert Kegan's theories of adult development helped me understand people better and be a much better coach and manager (a good practical introduction is in Jennifer Garvey-Berger's "Changing on the Job"). And a book I really like for having a lot of condensed wisdom is Laurence Endersen's "Pebbles of Perception".