I placed the planner on a corner of my desk. When I moved out of my dorm room the day after graduation, I left it there.

For the next two years, I remained anti day planner. I landed a job as an editor at a magazine, but my days were all uniform. What did I need to write down? “Work, 10 a.m. to 6 p.m.” Was there any chance I’d forget?

My plans with friends were made on the fly, our phone conversations ending in, “So, see you in an hour?” I figured if I couldn’t remember those rare events planned in advance, they must not have been that important anyway. My parents and people in business suits—they owned day planners. Me—I was more spontaneous.

But a promotion at the magazine meant longer, more unpredictable hours. I met an amazing guy, and wanted to spend 90 percent of my free time with him. My family moved to the city and I didn’t want to miss any of the plays, exhibits or restaurants they were always going to.

My nights and weekends became a mess. While I was out with my family, I’d get a voice mail from a friend saying, “It’s my birthday party. Where are you?” I was descending the slippery slope toward becoming a flake.

Then I hit bottom. I had tickets to see a favorite band play. When I arrived at the venue and handed my ticket to the bouncer, he looked at it, and back at me. “Sorry,” he said. “That was last night.”

“Last night?” I said. “It’s the 28th. Tonight.”

“Get a calendar,” he said. “It’s the 29th.”

I walked down the sidewalk despondent. Last night? Last night? I hadn’t done anything besides watch reruns. I couldn’t keep my schedule in my head anymore. I was going to have to give in and get a day planner.

The next morning I headed to an office-supply store, where I found the “Calendars and Planners” section, shelf upon shelf of time carefully metered out on paper. There were desk calendars, fat appointment books, journals the size of granola bars. Was I a daily, weekly or monthly kind of girl? Did I want open squares or unrelenting lines? Day minder or day-timer?

Selecting a day planner made me confront my worst fear—I could no longer ignore the fact that I was an adult, that most of the hours in my days were in fact prescribed, that I was becoming my parents. I backed up slowly, contemplating a run for the exit.

“Can I help you find something?” a store clerk asked.

“Day planner,” I stuttered.

She looked at the shelf and picked up a small blue book. “Most people like the weekly,” she said. “This one fits in your bag.” I took the book straight from her hand and headed for the checkout line. It cost only $6.

I went home and furiously sifted through each crumpled Post-it in my purse, writing the information in the appropriate slot. I went through e-mails and wrote down exact times and addresses. And I didn’t stop there. I marked big goals—“Write a book proposal” and “Paint apartment.” I jotted down friends’ birthdays, holidays, anniversaries.

Instead of feeling hemmed in like I’d feared, I felt relieved. I would never forget anything in my busy, amazing life ever again. Sure, as the pages became crowded with words, it was obvious that I had a lot of obligations. But I could make sure that growing up did not mean the end of fun.

When I first received that graduation-gift day planner, it made me feel like a kid on the brink of drowning in the “real world.” I was terrified that I didn’t know exactly what I wanted to do, that I didn’t know what a 401(k) was, that I didn’t even know how to file my taxes. But now I realize that everyone feels that way. The big “adult” things—having a cubicle or office, coming home to a stack of bills, being called ‘ma’am’—none of them feels completely natural. To an extent, we all feel like we’re pretending. Sure, when I was a kid, I didn’t imagine myself as a grown-up with a day planner. But then again, I also believed in the tooth fairy.