Venus Williams refused to be downcast after losing to third seed Agnieszka Radwanska in the second round of the French Open on Wednesday, saying she was still on a learning curve after being diagnosed with an autoimmune disease.

Venus Williams of the US reacts during her match against Agnieszka Radwanska of Poland during the French Open tennis tournament at the Roland Garros stadium in Paris May 30, 2012.[Photo/Agencies]

"I am really positive and my team is proud of me," the seven-times grand-slam winner told a news conference after being soundly beaten by Pole Radwanska 6-2 6-3. "I just have only to go up."

Reaching the second round had boosted her chances of making the American team for the London Olympics - her primary goal - the former world number one said.

"This tournament for me was all about getting to the Olympics and if that happens for me, and I think the chances are good, then I come out the victor."

Venus, who pulled out of last year's US Open and this year's Australian Open because of Sjogren's Syndrome, a fatigue-inducing, chronic, illness, said she felt lucky despite her diagnosis.

"Obviously it is frustrating at times. I don't know if there is anything more mentally I can do at this point but there is a lot of stages to go through with this kind of thing.

"But there are a lot of people who have it a lot worse than I do. I am still playing a professional sport.

"I haven't gotten to the 'why me?' yet, I hope I never get to the 'why me?'. I am not allowed to feel sorry for myself."

Venus said she had changed her diet to fight the illness and was eating "a lot of sprouts and green juices and grains and that kind of thing, a lot less sugar than what I'm used to".

Huge support

Sister Serena, who made a shock first-round exit from Roland Garros on Tuesday, was offering huge support, she said.

"When I changed my diet, she changed hers too, which means it was less tempting things in the house. She even takes it a step further. She prepares stuff and cooks, whereas if there is no food there then I just won't eat."

Venus said she hoped to be able to defend her doubles title with her sister at the London Games, adding with a smile: "If I can get Serena to do all the work."

She would be happy to play in any event, she said. "I have to wait and see what I'm elected for. Maybe doubles and mixed is better for me, I don't know."

Smiling again, she added: "For me, any medal in any event, even if it was the javelin, that's a medal."

Venus refused to dwell on the details of Wednesday's hour-long defeat, saying: "It's just important to give credit to the people who win, and I didn't win."

Radwanska dominated the court and was 5-1 up in the second set before Venus began to fight back, winning the next game to love then breaking for 5-3.

With light rain beginning to fall on the Philippe Chatrier court, Venus was one point from winning the next game but Radwanska got to matchpoint when she scooped the ball over the American's head, leaving her standing. A forehand mistake by Williams finished off the match.

Venus said she had been upset by Serena's three-set defeat by Frenchwoman Virginie Razzano on Tuesday.

"It's hard for me because all my hopes are on her for this tournament. I wanted her to win. I wasn't sure that I could, you know.

"She's been playing so well on the clay. I think if she could have gotten through that match, it would have been, this tournament, a lot different for her, but that's sport.

"Thankfully she has like 20-something majors to keep her warm at night; I think she'll be fine."