Mumbai, (PTI) With films such as "Rajneeti", "Ek Tha Tiger", "Dhoom 3" and "Tiger Zinda Hai" to her credit, she may have become one of the biggest female stars in Bollywood, but Katrina Kaif says it is tough to feel completely "secure" in movie business.

Katrina believes film industry is changing rapidly and to stay relevant one needs to explore new arenas in the showbiz.

"I don't think you can ever feel 100 per cent accomplished and secure in your career because it is a rapidly changing industry. Things are changing so quickly. But now I do feel comfortable and confident here," Katrina told PTI, over phone from London, where she will be celebrating her birthday tomorrow.

"I have had a career that has been successful. Going ahead, you have to put in that much hardwork, keep performing and keep doing films in new spaces that are not only challenging but also interesting to audience," she adds.

Katrina reveals she is working on few original concepts and scripts.

"I am also working on few concepts, which have been on my mind. I am working and developing these ideas."

Her last release "Tiger Zinda Hai", opposite Salman Khan, was a blockbuster and earned over Rs 545 crore worldwide.

In her next two films, "Zero" and "Thugs of Hindostan", the actor has teamed up one again with Shah Rukh Khan and Aamir Khan, respectively.

Looking back at the year, Katrina says, it has been "fulfilling and gratifying for me".

"This year has been really good for me, 'Tiger Zinda Hai' did very well and it was a new film for the audience and people appreciated it. It feels great that 'Tiger' franchise continues to be a success."

"Aanand L Rai's 'Zero' is something on which I had a very fulfilling experience.He really helps you. It was a good learning experience. And then I have 'Thugs of Hindostan' with Aamir, Yash Raj Films and Victor with whom I have worked on 'Dhoom 3'. There is a definite possibility that both the films will step up... be the next level (in visual effects)," she adds.

There have been rumours that Katrina will be seen in "Rajneeti 2", "Krrish 4", Aditya Dhar's film with Akshay Kumar, but according to her, she has not been approached for any of these projects.

"The only film I will be working on next is the dance film by Remo D'Souza and there are few ongoing discussions but things are not finalised."

The dance drama also stars Varun Dhawan and the duo will soon start preparing for the project.

"It is a film on dance so the preparation and the kind of dance forms that we are planning to achieve it is not going to be easy. There will be lot of training. We will start training in the next few months and the shooting would begun by the end of the year," she says.