Every quarter, publicly listed companies like Apple, Microsoft and Pinterest reveal their earnings and targets for the coming 90 days. They report to shareholders, analysts and the media about their targets, revenue projections and areas of focus. 

A quarter, or 90 days, serves as a constraint that forces companies to review their progress and adjust the direction of the company, much like a ship captain checking his or her route. 

For example, during its last revenue report, Pinterest CEO Ben Silbermann explained his company is developing tools for small businesses that want to advertise on this network. 

The constraint of 90 days affects executives at all levels. Employees must report on their progress to managers and other team members and adjust their goals if off course.

Apply The Constraint Of 90 Days In Your Work

Ninety days is a useful constraint for personal productivity and creative work too. First, consider learning a new work skill, like coding or design. Unless you're getting paid for it and have lots of time, set aside at least 30 minutes each morning or evening to study lesson materials and practice this skill. 

That's just enough time to work through several lessons on a site like LinkedIn Learning or read a chapter or two from a relevant book. But it's not so much time that learning impedes the rest of your day.

You might find it difficult to set aside 30 minutes each morning for the first few weeks. However, if you do this every day for a quarter, you'll have spent up to 45 hours learning a new skill. That's more than enough time to acquire the basics. 

What's more, according to researchers, 90 days is also arguably ideal for forming or breaking a new habit. In other words, you can learn the basics of a skill or form a productive habit in a season.

Next, consider a big creative project like writing a book. Louise Dean is a Man Booker-nominated novelist and the author of four published works. Her most recent novel, The Old Romantic, was selected as an Oprah Book of the Week.

She teaches many aspiring writers how to pen their first novel, a project that many creatives procrastinate about for years. According to Dean, 90 days is the perfect amount of time for writing a painful first draft.

"Ninety days is lovely because you're in a season," she says. "Atmospherically, you're writing in the same place with the same sort of lighting and feeling."

"The worst thing a writer can do...is binge writing. You get a week or a weekend, and you write thousands of words, and then you don't write for weeks. Novels don't happen that way. They can't,"Dean says.

At the end of the quarter, much like the CEO of a publicly listed company, review what worked, didn't work and what you're going to focus on next. You could reflect in a personal journal or blog post or simply document some relevant personal metrics on a spreadsheet.

If you've just learned the basics of a new skill, don't stop now. Set a new challenge that builds on what you acquired or pick a complementary area of study. An aspiring designer, for example, could challenge themselves with creating a logo. 

Alternatively, if you achieved a creative milestone, you could decide to edit and rewrite that first draft during the coming quarter and set a deadline for sending it to an editor or agent.

It doesn't matter if you're the CEO of a Fortune 500 company or Me Inc. The constraint of 90 days will help you break a big meaty goal down into something digestible.