"These days I feel like I'm more centered and grounded than I've ever been," he tells the Associated Press.
The actor, who met Cyrus in 2010 on the set of their film The Last Song, admits he's gone through a lot since he moved to Hollywood from his native Australia five years ago.
"I've learned so much," Hemsworth, 23, says. "The first few years in L.A. were really tough and scary, but I had to figure things out for myself."
And that meant learning to deal with all the media attention during his relationship with Cyrus, 20, and after their relationship ended in September following cheating rumors.
"What I always keep in mind is that I know what the truth is and that's all that matters," he says. "I know I'm a good person."
Hemsworth – who recently admitted that he's not seeing anyone special – credits surfing and kickboxing with helping him to escape from the pressure, but he also credits his Catching Fire costar Jennifer Lawrence with helping him find balance.
"For a few years I went down a path where I forgot to be in the moment and enjoy the moment," he says. "But being around someone like Jen, who is so honest and laughs all day long, I am forced to be in the right now. I'm much happier."