Filmmaker Rakeysh Omprakash Mehra, known for his directorials like "Rang De Basanti" and "Delhi 6", confesses that his last release "Bhaag Milkha Bhaag" was one of the most challenging films that he had ever attempted.

For him, it was like going to school every morning.

"Bhaag Milkha..." was a biopic on the life of former athlete Milkha Singh, portrayed by actor Farhan Akhtar. Released July 5 this year, the film did a whopping business of over Rs.100 crore and also found acceptance from the audiences of all age groups and strata.

"It (working on 'Bhaag Milkha..') was like going to school every morning. It is very difficult to put it in words but I enjoyed every moment of it. We went out everyday to do our jobs and came back home thinking 'did we do well or not?', " Mehra said here Tuesday at the DVD launch of the film.

"But in all, it was a hugely learning experience. It was one of the most challenging films which I had attempted and I am glad that it worked out, " he added.

Mehra is now busy with his next project "Mirza Sahiba", a musical which is based on a folkore set in Rajasthan.