Serena Williams said her 'level of greatness' can hold her back because she's so critical of herself, even when she's winning

• Serena Williams admitted after her first round victory at the French Open Monday that she struggled with her performance because of the "level of greatness" she expects of herself.
• Williams beat fellow American Kristie Ahn in straight sets but was unhappy with her first set performance, which saw her win after a tie break.
• "I have put so much perfectionist into my habits that, if it's not perfect, then it's not enough for me," she said after the match.

Serena Williams won her first round match at the French Open in straight sets on Monday, but admitted she struggled to accept her performance in the first set of the match, because of the "level of greatness" she expects from herself.

Williams beat fellow American Kristie Ahn in straight sets — 7-6, 6-0 — in her opening match of the tournament, a rematch of the pair's meeting during the first round of the US Open earlier in September.

While most players would be happy to get through the first round in straight sets, Williams said after the match that she was not satisfied with allowing the first set to go to a tie-break, and that she wants to work on this mental part of her game.

"I have put so much perfectionist into my habits that, if it's not perfect, then it's not enough for me," she said after the victory, which took her into the second round of a Grand Slam she has won three times before.

"That is something I have been working on. I feel like I was able to get over that in the past couple of months.

"So, I feel like that has been what I needed to just understand that my level of greatness is sometimes crazy high and a win is a win."

Williams made 28 unforced errors in the first set of the match, according to tournament data, and only took it to a tie break by breaking Ahn in the penultimate game of the set.

After that close call, she said, she gave herself a talking to and came out for the second set with more confidence.

The plan worked, and she beat Ahn to love in the second set.

"The biggest difference was just confidence. I just need to play with more confidence, like I'm Serena," she said.

"So that was it. I just started playing like that. I love the clay and I started playing like it, opening the court and moving and sliding."