I suppose there should be things that really stick out in the mind, if there are true turning points. But right now nothing strikes me like that.
Let's see. Once I had a dearly admired professor who used my paper as an example of "how not to write a paper" -- that was a turning point in my education, and I became smarter for it.
Leaving Steve wa a big turning point. After six years of being together, I'd finally had enough, and went to live with my parents for a year and a half, and then finally on my own, for the first time in my life, back in 1988, and I have been alone (for the most part) ever since.