Mark Hamill pens goodbye letter to 'Star Wars' co-star Carrie Fisher

Original "Star Wars" cast members Peter Mayhew (L), Mark Hamill, Carrie Fisher and Anthony Daniels (R) appear at the kick-off event of the Star Wars Celebration convention in Anaheim, California, April 16, 2015. The Star Wars Celebration runs through April 19 at the Anaheim Convention Center. REUTERS/David McNew - RTR4XNYR

Mark Hamill has penned a heartfelt — and brutally honest — goodbye to longtime co-star and friend Carrie Fisher.

The actor, best known for his role in “Star Wars” as Luke Skywalker, opened up in an essay for The Hollywood Reporter on Monday about what it was really like to be Princess Leia’s brother for nearly four decades.

“When you were in her good graces, you couldn’t have more fun with any person on the planet … And then you could go 180 degrees opposite, where you were furious with one another and wouldn’t speak for weeks and weeks,” Hamill wrote.

“But that’s all part of what makes a relationship complete. It’s not all one sided. Like I say, she was a handful. She was high maintenance. But my life would have been so much drabber and less interesting if she hadn’t been the friend that she was.”

Fisher died on Dec. 27 at age 60 after suffering a heart attack four days earlier during a flight from London to Los Angeles. Hamill remained relatively quiet following her death, tweeting that he was “devastated” by the loss and later posting a short tribute on Facebook.

In the Hollywood Reporter piece, he described how despite having its ups and downs, his relationship with Fisher was one he deeply cherished.

“She was able to make you feel like you were the most important thing in her life,” Hamill explained. “I think that’s a really rare quality.”

The pair met for the very first time at a dinner the night before they began filming “Star Wars” — and Hamill recalled how he had been completely “bowled over” by Fisher.

“I mean she was just so instantly ingratiating and funny and outspoken. She had a way of just being so brutally candid,” Hamill said. “I’d just met her but it was like talking to a person you’d known for ten years. She was telling me stuff about her stepfather, about her mom, about [her father] Eddie Fisher — it was just harrowing in its detail. I kept thinking, ‘Should I know this?’ I mean, I wouldn’t have shared that with somebody that I had trusted for years and years and years. But she was the opposite. She just sucked you into her world.”

Fisher was just 19-years-old at the time, and Hamill “a worldly 24” — but the actress was in a league of her own, he said.

“I was just in awe of her,” Hamill wrote. “She was so committed to joy and fun and embracing life. She had an Auntie Mame quality to her. I would do crazy things to amuse her on the set. Making her laugh was always a badge of honor.”

Despite having a close relationship, the actor admitted that him and Fisher tended to butt heads.

“We ran the gamut over the years, where we were in love with each other, where we hated each other’s guts,” Hamill said, remembering how they’d say things to each other like, “I’m not speaking to you, you’re such a judgmental, royal brat!”

“We went through it all,” he wrote. “It’s like we were a family.”

Hamill said the on-screen siblings remained thick-as-thieves long after the release of the first three “Star Wars” films.

“I’m grateful that we stayed friends and got to have this second act with the new movies,” he explained. “I think it was reassuring to her that I was there, the same person, that she could trust me, as critical as we could sometimes be with each other.”

This article originally appeared in Page Six.