In "Spider-Man: No Way Home" Tom Holland plays a superhero who fearlessly swings from buildings and battles powerful villains — but in real life, the British actor has struggled with his confidence. 

Speaking to GQ magazine, Holland, 25, shared that earlier in his career, he'd often feel scared or nervous to start a new project. "As a kid, a lot of my confidence was really fake," he told the publication. "But, really, inside I was, 'Oh, my God, I'm … terrified.' " 

Holland was cast as Spider-Man in 2015 when he was just 19 years old, appearing in 2016's "Captain America: Civil War" before starring in 2017's "Spider-Man: Homecoming" alongside superstar actors Robert Downey Jr., Michael Keaton, Zendaya and others. "Spider-Man: No Way Home" premiered in theaters across the United States Thursday night and is expected to bring in about $200 million during its opening weekend, CNBC reports. 

To calm his nerves on set, Holland says he learned to convince himself to focus on feeling excited instead. "I was given this piece of advice as a kid that was really helpful, which is: If you think about the actual physical feeling of being nervous, it's the same physical feeling as being excited," he said to GQ.

Still, Holland recalled sometimes feeling burned out as his acting career took off and couldn't figure out how to set better work-life boundaries. But Elizabeth Olsen — who co-starred with Holland in "Captain America: Civil War" and the Avengers movies, helped teach the actor how to stand up for himself. "She gave me an amazing piece of advice: 'No' is a full sentence …'No' is enough'" he told GQ. 

Holland turned to that advice during the international press tour for "Spider-Man: Homecoming," which saw him travel to 17 countries. When he got to the tour's last stop, China, Holland said he was "really ill." "But I didn't say no," he added.

During a press conference, Holland reached his breaking point: he left the stage and threw up. "I was under a lot of pressure to finish the day's work," he said. "That was the first time I was really like, 'No, I'm done now. I've given you everything.' "

Holland added that people often mistake his kindness for weakness. "Let me tell you, when you're a 19-year-old kid, they really do take advantage of you … you don't know any better," he said during his GQ interview. "Now I look back and go, 'Wow, I wish someone had told me that I could say no.' "

While he was shooting the final scene for "Spider-Man: No Way Home," Holland once again turned to Olsen's advice. "I kept stopping [the shoot] and being like, 'I'm so sorry, I just don't believe what I'm saying,' " he told GQ. 

Director Jon Watts pulled Holland aside to discuss the scene, and they came up with a new idea together. "Then we pitched it to the writers, they rewrote it, and it works great," he said. 

Next, Holland is slated to star in the action film "Uncharted," which will premiere in February, and will portray Fred Astaire in an upcoming biopic about the entertainer. 

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