Actor Sunny Deol says he is the biggest critic of his work and knows it very well when his performance is not upto the mark.

The 57-year-old has been a part of movies like "Darr", "Gadar: Ek Prem Katha" and "Yamla Pagla Deewana".

"I am my biggest critic. I know best where I am right and wrong. At times you will not see me happy when people say, 'Wow, what a shot'. I feel, 'What was this, I didn't deliver what I want to'," said Sunny, whose latest movie "Singh Saab The Great" released Friday.