During the brutal oil recession in 2015 and as Halliburton faced billions of dollars in losses, Miller was forced to cut 35,000 jobs—nearly half of the energy company’s workforce.

“That was the hardest thing I’ve ever had to do,” says Miller, who spent a lot of time in the oil fields explaining to Halliburton employees why the company needed to take such drastic cuts. Speaking with Fortune’s Susie Gharib, Miller says that crisis also taught him an important leadership lesson.

“The learning in that was that we had to do the next right thing even when the next right thing may not be tasteful,” he says. “It’s just something that had to be done.” A Dallas native, the loss hit Miller close to home. In his 20 years at Halliburton, he had worked an array of jobs, from finance to operations. His diverse resume gave him a unique perspective on the value of the jobs lost.

“I think I had empathy for everyone in the company,” he says.

Things are looking up now that the oil industry is recovering. Halliburton revenues surged 30 percent to $20 billion in 2017, bumping the Fortune 500 company up 27 spots to number 146 on the list of America’s largest companies. Thanks to those economic gains, Halliburton is hiring again, including bringing back many of those who lost their jobs during the downturn. In good times or bad times, Miller still makes a point to regularly visit workers on the field in search of feedback.

“I think I make better decisions when I’m clear around not only what’s really happening but how it affects other people,” he says.

Watch the video above for more from our interview with Miller.