Yes, that is a picture of me attempting to rap in front of a group of students. (I’m not sure if others were laughing at me or laughing with me – luckily, there’s no video footage from those pre-iPhone days to prove one way or the other – but I certainly had fun trying.) This experience was part of my first job out of college, as the founder and executive director of a non-profit called Summerbridge Pittsburgh, now part of Breakthrough Collaborative. It’s also where I learned some of the most valuable advice of my career.

Breakthrough is a “students teaching students” model, with the mission to launch high-potential, low-income middle school students on the path to college and to inspire high school and college students to pursue careers in education. During the school year, I spent part of my time teaching high schoolers and the rest of my time raising money, recruiting new students and staff, and preparing operations for our after-school and summer programs.

Each summer, 100 seventh and eighth graders, along with 30 high school and college-aged staff, would arrive. It was joyous and high-energy, filled with rigorous academic classes and skits, cheers, and spirit stick awards. It was like magic.

The only problem was that making that magic happen took a hell of a lot of work – so much work, in fact, that I lost control of the rest of my life. It was easy for me to see this because every day, I carried around a piece of paper with me in my pocket that listed items I needed from the drugstore: shampoo, vitamins, you get the idea. And every day, the list got longer, because the drugstore closed at 9 p.m., and I never left work before 9. Simply put, I had no time for life outside of work.

Then one day, midway through my first summer running the program, I got a visit from an incredible woman named Lynn Sorensen, then a program officer at the national Breakthrough Collaborative and now the executive director at the TEAK Fellowship.

Lynn looked at me, an ever-growing list of unpurchased drugstore items in my pocket, and asked me why I didn’t leave work earlier. I told her I couldn’t because the staff was still working past 9, and I had to stay until they were done; I was the only person with the keys to the building. That clearly was not a reasonable answer in Lynn’s mind. She explained to me that it was my responsibility as the leader to set the right example for the staff and to help them (and myself) understand the difference between work that was really important and work that wasn’t.

She taught me an extremely basic technique, “mission-based prioritization,” that I still use to this day. (Even 20 years later, there are still times when I find myself needing to remember to do this.) Here’s how it works: make a grid with your mission statement at the top (or whatever language you use to measure your primary work objective) and your “to-do” list down the side. Run through your entire to-do list, checking whether each item does or does not impact your ability to achieve your mission.

For Summerbridge, where our mission was to launch students on the path to college, this meant that items on my list like “review algebra lesson plans” were in the “yes” column, while tasks like “call vendors about pricing for summer t-shirts” were in the “no” column. Would great summer t-shirts be nice? Absolutely. Were they necessary to make sure the students were prepared for rigorous high schools and 4-year colleges? No.

It’s not that only serious work made the “mission” list. Some of the fun things did, too, since part of the goal of the program was to ensure kids had so much fun learning that they wanted to keep learning throughout their lives. For example, tasks like rapping about my students’ incredible achievements at our end-of-summer celebration still made the list, and Breakthrough wouldn’t be the same without them.

Similarly, at Facebook, I now prioritize based on our overall company mission to give people the power to build community and bring the world closer together. That means that my final to-do list could still include everything from planning our product roadmap to hiring amazing people to, yes, making fun of myself by singing at company events (though I have yet to rap again).

Back at Summerbridge, with Lynn’s wisdom, I was able to let go of some of the less mission-critical items on my list and help my staff to do the same. We all started going home before 9 p.m. (well, on most nights, at least), I got my shampoo and vitamins, and I even found time to take dance classes, where I eventually met my husband. And, we delivered on our mission – more than 90% of our students did, in fact, attend and graduate from college.

As it turns out, by removing some of the less important work from our lists on a daily basis, we did have time for some fun extras. In the photo below, you’ll see me with some of my incredible and quite successful former students at Summerbridge Pittsburgh’s 20th reunion a couple summers ago. If you look closely, you’ll see that one of those students is wearing a 1994 Summerbridge t-shirt, signed by all his friends that year. With smart prioritization, we managed to get the shirts made after all.

This post is part of a series in which LinkedIn Influencers share the best advice they’ve ever received. Read all the posts here.