Facebook Chief Product Officer Chris Cox knows you get frustrated when Facebook changes your News Feed too much--but the social networking site isn't stopping experiments any time soon.

Bloomberg Business published an interview today with Cox, the executive responsible for testing out user reactions to changes in Facebook's News Feed. Most recently, Cox and his team have been getting ready to roll out Reactions, emoji-like buttons that will allow Facebook users to react to posts in more ways beyond just pressing a 'like' button. In a few weeks, people will be able to react engagement announcements and baby photos with "Love," "Haha," Wow," "Sad," and "Angry."

It's no easy task--as Bloomberg's Sarah Frier puts it, "changing the button is like Coca-Cola messing with its secret recipe."

But Cox has managed to stay cool under pressure and maintain his position as one of Facebook's most influential behind-the-scenes employee. Here's how Cox has found ways to change Facebook's core products, without alienating customers.

1. Stay empathetic.

Cox's coworkers often describe him as "the voice for the user." Mark Zuckerberg says that one of Cox's best qualities is his emotional intelligence--a skill he honed while serving as Facebook's human resources chief.  While he was originally hired as a developer to work on Facebook's News Feed, as the company reached 100 employees, Zuckerberg realized that Facebook needed a formal human resources department, and put Cox in charge of it.

Cox made it a top priority to meet one-on-one with every employee, essentially working as the "in-house therapist." The experience "gave him a way of looking at things through other people's eyes."

2. Test out the change first.

When Facebook announced that it was launching beta testing for Reactions in October, the site had originally planned on releasing six different emotion buttons. However, the sixth reaction, "Yay," was axed during testing. Facebook's beta testing, done in multiple countries, revealed that "Yay" was not universally understood. Make sure that your beta testing captures a diverse cross-section of users. 

3. Be honest.

Not all of Cox's experiments at Facebook have been a success. He was also the man behind Paper, a news app that received good reviews, but hasn't gained much traction. But Cox doesn't look back on his failures with regret. "I think any good company is trying things," Cox told Bloomberg. "People only get in trouble if they're not honest about failure."

4. Know your customer's 'rage quit' point.

Bloomberg followed Cox and his team while they were developing the Facebook India app. One of the biggest challenges Facebook faced in developing an app for users in India was the country's extremely slow Internet speeds--only 0.2 percent of Android users have 4G internet speed, the fastest wireless network available on mobile phones. A March report from wireless coverage mapping site OpenSignal found that 77 percent of the U.S. smartphone owners that they surveyed used a  4G network

Cox realized that a slower wireless network meant that Facebook had to use less data and proposed adding an icon that would let users know that a photo was taking a long time to load. Cox hoped that this would result in fewer users quitting the app, frustrated because they didn't know how far a page was into loading. Fittingly, Cox calls these instances "rage quits."