Linda Hamilton Jokes She Was a ‘Hot Mess for the First 40 Years’ of Life as She Reflects on Her Mental Health (Exclusive)

Linda Hamilton is getting candid about her decades-long mental health journey.

The actress spoke to PEOPLE exclusively about everything from becoming a grandma to her new sci-fi film, Osiris. During the conversation, Hamilton — who has opened up about her experience with depression and bipolar disorder in the past — said that her action-star persona often makes people believe she’s invincible in real life as well.

“Nobody ever thinks that I’m going to struggle. [They think] I’ll be fine — ‘It’s Linda Hamilton,’ ” the actress, 68, says.

However, she went on to say that she’s currently in a solid place — in no small part due to years of working on her mental health. “I have found just true balance and steadiness in my day and in my life,” the Stranger Things actress shares. “And I also can activate all of the safeguards that I learned from 20 years of therapy.”

“If I’m having a bad day, that doesn’t mean that my behavior has to be bad or that my actions [have to be],” she explains, adding, “I’m experienced enough now to go, ‘Well, [doing] that might sound good right now, but really in an hour, are you going to want to have done that?’ ”

“I can apply the brakes because I spent years and years and hundreds of thousands of dollars to get better,” she continues.

The Terminator 2: Judgement Day star also shared encouraging words for others who might be struggling with their own mental health. “People just can’t give up on themselves. That’s the thing. It’s just keep looking until you find your way through it. I’m living proof that it can be done,” she says, before joking, “And I was a hot mess for the first 40 years.”

Hamilton adds that she’s found peace by attempting to place greater focus on the needs of others. “I never think about myself. That was the first 40 years […]. And when I got the balance […] I made a deal with myself that it would never be about me again. And it hardly ever is. It’s just not about me.”

Never miss a story — sign up for PEOPLE’s free daily newsletter to stay up-to-date on the best of what PEOPLE has to offer​​, from celebrity news to compelling human interest stories.

“I want to pitch in, help people, make people laugh, make my house beautiful. The normal things. Love my dogs to death. [And] it all makes me very happy,” she says.

The actress, who first broke out in the 1984 sci-fi action epic Terminator, publicly revealed that she had both bipolar disorder and depression in 2004. “I would say [I had] 20 full years of symptoms, not counting my childhood. From 20 to 40. I call them my lost years,” she said in an exclusive interview with AP Radio at the time.

She also shared that she had intense mood swings, though didn’t understand why at the time. “My first husband [actor Bruce Abbott] said you have the most incredible joy and the most incredible sorrow that goes with it. Without giving it a name, he had pretty much summed it up for me,” she recalled.

She went on to describe her manic episodes as feeling like “an amazingly brilliant time” — with severe consequences. “You don’t need sleep. I think I existed on four hours sleep a night for four years. Sleep doesn’t seem necessary. You wake up feeling great. But it’s not all great feelings. A lot of the raging that I did I think was the manic part of my disorder,” she shared.

“The capacity for fighting, war, taking everything on, taking too much on, overachieving and then raging because my system was so depleted,” she recalled.

Hamilton went on to say that she had decided to speak publicly about her experience in the hope of helping others. “I want to destigmatize the words mental illness,” she told AP Radio. “Somebody needs to come out and make this okay for people to talk about and get help and take advantage of the resources.”

If you or someone you know needs mental health help, text “STRENGTH” to the Crisis Text Line at 741-741 to be connected to a certified crisis counselor.