I can clearly recall why I became a computer scientist. I was sitting in a class and we were discussing how cons was implemented. And then I saw this definition:

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(define (cons a b)
    (lambda (x)
        (if (= x 1) a b)))

(define (first l)
    (l 1))

(define (rest l)
    (l 2))

The lambda calculus and the material in the little schemer kept me in the field (computer-science i.e.) and assured me that there would never be a dearth of aha! moments in my education.

Good educators can deliver such aha! moments in every single lecture. A good textbook can do it several times each chapter.

I have since tried to find material that delivers such aha! moments.

Hopefully, I will encounter them for the rest of my life in whatever I do.