I just celebrated a milestone birthday. I can sum it up in four words: “How did this happen?”

I respect birthdays, and I always give myself permission to spend them doing whatever I want. This year, however, pinpointing that was hard. Nothing felt worth the effort.

It took a while to realize that what I really wanted was unattainable. You can’t re-insert yourself back in time.

Despite that, I woke up on my birthday knowing that I wanted to walk.

I started from home, heading toward the town where I’d attended college. That university was the beginning of why I live where I do now. I’m not from here and never intended to stay.

Many of the buildings that existed back then are gone, but they lived again for me, superimposed against the urban revitalization that now occupies their space. I followed the route I’d once taken daily, from the house I shared with housemates I enjoyed, past the magazine-store job that brought me excellent friends (and hardly any money), down along the main street to the university.

One era merged into a slightly earlier one as my route continued past the apartment I lived in when I first arrived for school. Impressions of the university were stronger here, along with the uncertainty of living on my own for the first time. The school has expanded, filling up once-empty spaces and gobbling up many of my old haunts.

I passed through a friend’s neighborhood and remembered his exuberance and endless trove of stories. A walk like this can’t help but call up shadows of people who were once major parts each day and now exist only in memory. I wondered how their stories evolved, how the rest of their lives unfolded. I considered reaching out — that’s both the pro and the con of the internet, after all; answers are just a Google search away. But sometimes there are good reasons why people have drifted into memory, and if you wouldn’t contact them in person, maybe it’s best to leave things the way they are.

I left my college days and entered the outer orbit of places my very young children and I traveled when running errands from home in the city. My sweet girls were usually happy, ready for adventures at the grocery store or playground, lighting my world just by being in it.

I’d been right, of course. You can’t immerse yourself in memory. Recollection itself changes as layers of experience and understanding deepen our perspective of even events we thought we knew well. I think we’re supposed to do that. There’s beauty in studying the fabric of our lives and finally seeing purpose in the design.

But time is more spiral than linear, and my walk had never been about visiting the past in the first place. Re-circling my younger self in all her vital, naïve glory has its wince-worthy moments, but she also possesses attributes I could use now. I need her hope, her fierceness, her sense of possibility as the whole world opens before her. I need to re-introduce myself to her so that energies of past and present can flow together in clarity and strength for this next uncertain leg of the journey.

We’ll see how I do.