"I can't even believe it," she told Variety.
"It's interesting, because I have all kinds of impostor syndrome. I've always felt like I'm supposed to struggle, I'm supposed to keep proving myself, and this sort of just came out of the blue. It's really lovely."
Watts has been nominated for numerous accolades during her career, including two Academy Awards and two Golden Globe Awards. But the actor struggled at first to find success in Hollywood.
"I pretty much was deemed as unhireable. I was flunking auditions over and over again, or I'd get in a movie and it would get cut down or out. It was just bad luck," she said.
Watts said her early struggles have actually made her recent success even more meaningful, including the Walk of Fame star.
The actor has starred in films such as St Vincent, Birdman and While We're Young.
"I struggled for so long. I'm so familiar with that side of things more than this incredible good fortune, celebrations like this. It's wonderful," she explained.
Watts, who was born in the UK before moving to Australia in her teens, told the Guardian newspaper: "I had $2000 to my name and one phone number belonging to a friend of my mother's."
"And I was friendly but not yet besties with Nicole Kidman. We'd worked together on Flirting, and we knew each other peripherally from back home in Australia. We became much better acquainted once I moved here. And over time I made more friends and built a community.
"The point is: I was brave back then. So I can be brave now when it comes to taking risks in life."
Watts also stressed the importance of working with talented directors who share similar values.
"Working with people whose values you share makes everything so much easier," she said.
"I believe that film is ultimately a director's medium, so I've always done my best to find directors I trust and to put myself in their capable hands. Of course, it's a collaborative experience, but the director is the main storyteller. As an actor, you have to give yourself over to their point of view as much as possible.
"You don't always have that luxury when the A-list directors stop calling - which has been my experience for years at a time. Maybe that's because I've had a few bombs along the way. More than a handful!"
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