The seven-time Formula One champion Michael Schumacher has admitted that he had doubts ahead of his historic comeback, but says uncertainty is a secret to his success.
Schumacher says he even had doubts during his good years, but that forces him to constantly look for new areas to improve on.
The 41-year-old will race in the season-opening Bahrain Grand Prix this weekend following a three year hiatus, where four world champions will line up on the starting grid for the first time in 11 years.
