The actress was shooting for her upcoming film "Tanu Weds Manu Returns" when she got the news.
"This award is special for me. I had no clue about it because a day before I was busy with my birthday and the poster launch of 'Tanu Weds Manu Returns'. It's a real thing for me because unlike other awards there was no pre-nomination party and 'ho halla' about it," she told PTI in an interview.
Kangana was a front-runner for the honour for her powerful-yet-subtle portrayal of a traditional girl who goes on a journey of self-realisation after being ditched at the altar in the Vikas Bahl-directed movie.
"To be honest, I really don't remember the day I won my first National award. I was watching TV and came to know that I won it. I was young at that time. I am glad that 'Queen' connected everyone. I think the cheer from the people when the award was announced on March 24th was something which all actor wants," she said.
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The "Gangster" star, who faced a lot of criticism for her accent and fashion style initially, is happy to have made a successful career and wants to be more careful while selecting her future roles.
"I am careful with my projects. I will choose my future roles with a lot of thought now," she added.
Post "Queen", Kangana has been on a career high as she has a chock-a-block diary filled with interesting projects, most recent one being the sequel of "Tanu Weds Manu" which releases on May 29.