Kim Clijsters’ singles professional tennis career came to an end in the second round of the U.S. Open Wednesday (August 29th), when she lost to Britain’s Laura Robson 7-6 (4), 7-6 (5). The four-time Grand Slam title winner will retire after she finishes playing in the U.S. Open’s doubles tournament. Speaking after yesterday’s match, the 29-year-old Belgian said, “It’s been an incredible journey, and a lot of dreams for me have come true because of tennis.” Clijsters had retired before, in May 2007, only to return more than two years later, but now says she’s ending her career for good. Clijsters won the U.S. Open in 2005, 2009 and 2010, and the Australian Open in 2011. Three of those four Grand Slam titles came after she returned from retirement. In other play yesterday, winners included Victoria Azarenka, Maria Sharapova, defending women’s champion Sam Stosur and Andy Murray.