Lovato, who guest hosted the episode, said she was inspired by Bieber following her 2018 overdose and hospitalization.
"For me and my experience, when I struggled last year, I know I looked at you as an inspiration, because you've been through this and you've come out the other side," she told Bieber. "I really just admire the man you are today."
"I think for a while, I tried to run away from some stuff," Bieber said. "I tried to run away from the industry, tried to run away from what I felt like God wanted me to do. But I feel like this is what you and I are both meant to do -- you're meant to entertain and sing, and I think same as me."
"When we run away from that, it's almost like we come less happy. Then we feel like there's all these responsibilities, and all these sort of things that become heavy for us," he added. "I think sometimes we have to run towards the pain, rather than run away from it."
Bieber encouraged people to be vulnerable and "open and honest" about their problems.
"I think the more mature you become, the more you understand that there's power in your weakness," he said. "When you're able to show that, it gives other people the confidence to say, 'You know what? I'm going through similar things myself.'"
On Thursday's episode of Ellen, Lovato discussed her relapse with alcohol and drugs and her struggle with an eating disorder. Lovato recalled how her former management team "controlled" her diet, which contributed to her issues.