It was a summer romance that has come to an end. Entourage star Jerry Ferrara, 32, and Gossip Girl actress Katie Cassidy, 25, have ended their relationship, a source close to the couple tells Life & Style."It was a mutual decision, but its still hard," the source tells Life & Style. "The distance was just too much. She's shooting [the TV series] Arrow in Canada, and he's going off to do a movie [Las Vegas] with Robert De Niro in Vegas and then Atlanta."The couple started dating at the beginning of the summer and things heated up after a trip to the Four Seasons in Hawaii in July. "They really liked each other and she had spent a lot of time with his family," the source adds. "It definitely didn't end badly though. He's good at staying on good terms with his exes, like Jamie-Lynn Sigler."