I turned 25 today.

As I do most days, I walked into the bathroom, made some funny faces in the mirror, and then took a long hard look at myself.

I never look any different than I did the night before. I never feel much different either.

I suppose that’s the thing about change. It usually happens far too slowly to be noticeable. But day by day, year by year, decade by decade, things most certainly change.

There’s no denying that I look quite a bit different today than I did 10 years ago. I like to think I’ve learned a thing or two along the way as well. But as I walked into the bathroom today, for the first time finding myself closer to age 40 than to age 10, I couldn’t help but feel like for the majority of my life, I had been looking in the wrong mirror.

Over the course of the last few years, I’ve become far less interested in the physical aspects of my evolution and far more interested in the emotional, intellectual, and (dare I say) spiritual aspects.

I still don’t exactly know how I would define “spiritual evolution.” I do know however that I have increasingly found myself caring less about what other people think of me and more about what other people think of themselves.

Maybe I’m evolving spiritually. Maybe I’m a recovering narcissist. Maybe it’s a little bit of both.

Naming conventions aside, I’ve often struggled to document the non-physical facets of my personal evolution, while finding it frustratingly easy to document the physical ones. I can pull up any old picture and see, quite clearly, how my appearance has changed over the decades. That exercise is however far more entertaining than it is interesting.

Over the course of the last few years, when I haven’t been busy making funny faces in the mirror, I’ve spent a lot of time reading. In aggregate, I’ve read hundreds of thousands of sentences across all sorts of media — books, tweets, articles, work emails, iMessages, Amazon reviews, you name it.

Now, I don’t mean to sound dramatic (and I definitely don’t mean to offend any colleagues or fellow Amazon reviewers), but of all of those sentences, there is one that has stood out above the rest. One that has secured the title of “most important sentence I have read in a long time.”

It goes like this.

Books are like mirrors, you only see in them what you already have inside you.

I can’t explain why I am so taken with this sentence until I explain why seven-year-olds shouldn’t read Shakespeare…so here goes.

To be fair, there are probably a lot of reasons why seven-year-olds shouldn’t read Shakespeare. Most people would probably tell you the main reason is that seven-year-olds’ reading comprehension abilities aren’t advanced enough to comprehend the prose. Unfortunately, that’s not that interesting of an answer.

If you asked me why seven-year-olds shouldn’t read Shakespeare, I would tell you it’s because they haven’t had enough life experiences (nor have they developed the faculty to integrate their life experiences in a way that is novel, narrative, and/or unique), for Shakespeare’s poetry or plays to mean anything to them.

Most seven-year-olds have never experienced love, loss, regret, or betrayal. And it is precisely because of this lack of life experience that if you were to hold up one of Shakespeare’s plays in front of them, the metaphorical mirror would not reflect a whole lot of anything.

So what do seven-year-olds and Shakespeare have to do with my expedition to understand the wonderfully mysterious process of becoming myself?

Without mirrors or photographs, I would struggle to take stock of the evolution of my physical features — my outer self.