Recently I referenced having watched a PBS documentary titled Understanding, about the function of memory, how they're created, stored, and revisited, and the way memories affect perception and shape perspective. It's believed that all memories are registered in the brain, every memory makes a lasting impression, though many quickly become lost because they aren't stored for retrieval; nevertheless, they're in there. Some build and affect slowly over time, others are so dramatic and create such strong impression they actually affect the hard-wiring of the brain, in a dramatic and lasting way. It's a very real, physical process.
Of course the experiences we have in early youth are the most critical and influential because the brain is still so young and forming, impressionable. Though all throughout life the brain is barraged by new input, sometimes so powerful they can immediately affect the hard-wiring of the brain. Extremely traumatic instances can be so shocking. In December of last year I was so severely shaken by a sudden realization (resulting from convergence of elements) that my entire direction was off course, a seizure of some sort resulted, and nothing has been the same since. Something snapped, literally, and I can't ever go back to the previous way of thinking. In retrospect that was a good thing, though uncomfortable and unsettling, as life changing events will be. I think more difficult to adapt to as we grow older, because so many other brain connections are already established, and have to adjust accordingly.