Facebook chief operating officer Sheryl Sandberg addressed the Massachusetts Institute of Technology Class of 2018 today, using the recent Facebook data scandals as a warning about the potential issues facing graduates.

The social media service has been under fire as revelations emerged that it has been sharing user data in ways that shocked many account holders. Sandberg herself drew criticism for staying silent in the first few days after the Cambridge Analytica scandal unfolded before emerging with an apologia that left many unsatisfied.

Beyond that issue, it became clear that Facebook had left people’s personal information open for mining by third-party app developers and certain device manufacturers. That has led to some advertisers leaving the service and some users deleting their accounts.

While noting she is proud of what Facebook has done around the world, Sandberg admitted, “we didn’t see all the risks coming, and we didn’t do enough to stop them.”

“It’s painful when you miss something, when you make the mistake of believing so much in the good you are seeing that you don’t see the bad,” Sandberg said. “It’s hard when you know that you let people down.”

Sandberg used the experience to point out what a mentor once told her: “Smooth seas never make good sailors.”

‘The times in my life that I have learned the most have definitely been the hardest. That is when you will learn the most about yourself. You can almost feel yourself growing; you can feel the growing pains. When you own your mistakes, you can work harder to correct them and even harder to prevent the next ones.”

Regarding the potential next ones, Sandberg said changing technology requires recognizing “the full weight of our responsibilities. It’s not enough to be technologists, we have to make sure that technology serves people. It’s not enough or even possible to be neutral. Tools are shaped by the minds that make them as well as the hands that use them.”

She added: “It’s not enough to have a good idea, we have to know when to stop a bad one.”