In an interview with The Guardian Wednesday, the singer, 27, spoke about losing both his mom and sister within a little over two years.
Tomlinson's mother, Johannah Deakin passed away from leukemia in December 2016. Last March, his 18-year-old sister, Félicité, was found unconscious at her apartment and couldn't be revived. Earlier this month, it was revealed Félicité died of an accidental overdose and had been taking anxiety medication following the death of Johannah.
"That whole dark side I've gone through, it sounds stupid to say, but it gives me strength everywhere else in my life because that's the darkest shit that I'm going to have to deal with," Tomlinson said. "So it makes everything else, not feel easier and not less important, but, in the grand scheme of things, you see things for what they are, I suppose.”
The One Direction alum explained how his fans have been a strong support system for him during this difficult time.
"I'm sure every artist says this, but I do believe it," he said. "We've been through some dark times together and those things I've been through, they carry a weight, emotionally, on the fans as well. And I felt their love and support. I remember really clearly when I lost my mum, that support was mad."
Throughout the devastating losses of his sister and mother, Tomlinson has learned a lot about himself.
"I keep going back to it, but I don't know if it's a combination of where I grew up and my mum's influence, but I just have this luxury of being able to see the glass half-full no matter what," he explained, adding that since he's the oldest of his mother's children, "there's no time for me to be sat feeling sorry for myself."
He added, "I've been to rock bottom and I feel like, whatever my career's going to throw in front of me, it's going to be nothing as big or as emotionally heavy as that. So, weirdly, I've turned something that's really dark into something that empowers me, makes me stronger."
The pop star, whose debut album will be out next year, also spoke about his single "Two of Us," which is about his mom's death.
"After I lost my mum, every song I wrote felt, not pathetic, but that it lacked true meaning to me," he said. "I felt that, as a songwriter, I wasn't going to move on until I'd written a song like that."
"It was like the song I always wished I'd written," he continued. "I went in and put my personal touch to the verses. It was a real moment for me in my grief, and as part of the creative process, because it felt like it was hanging over me."