A little background is necessary for this one: Gordon Cooper, the last Mercury astronaut had a complete electrical failure - everything but his radio dead, no instruments, no control system - while in orbit. The capsule wasn't designed for pilot control so he had to manually operate the boosters with a watch and the fuel valves. After nearly dieing in space:
"... that's really what we'd been wanting to do all along. So, it just gave me the opportunity to do what we'd been wanting to do."