Lewis Hamilton admitted the pressure is on him to improve after his Mercedes team-mate Nico Rosberg won the Monaco Grand Prix.
Rosberg's victory came after three consecutive pole positions, and was the second successive race in which he has beaten Hamilton on Sunday.
Although Hamilton dropped from second to fourth when the safety car emerged in the middle of the pitstops, he denied he had been unlucky.
"I don't put it down to bad luck," Hamilton insisted.
"I wasn't good enough this weekend.
"Big congratulations to Nico and the team, they did a great job today and I have to keep work harder."
Hamilton conceded that he had miscalculated the gap he should leave to Rosberg when they both had to pit on the same lap during the safety car.
Red Bull duo Sebastian Vettel and Mark Webber were able to get between the Mercedes as a result.
"It was my mistake today," Hamilton said.
"I was told to have a six-second gap, and I had a little more than six seconds and I lost out. That's motor racing."