Amy Winehouse has vowed to stay sober on stage for her European tour.The 'Rehab' singer - who cancelled several dates when she was hospitalised in August after a drugs overdose - pledged not to drink before going on stage after the run of shows got off to a disastrous start on the opening night.At last week's Berlin concert Amy forgot the lyrics to some of her songs and stumbled on stage. She was then arrested for possession of cannabis in Norway.A tour insider said: "This tour started pretty much as the last one ended. Berlin was a difficult time for everyone and we thought it was going to turn into another tour full of drunken and missed shows."But she has now said she will not drink before shows for the rest of the tour."She stuck to it in Amsterdam, amazingly, and gave her best show of the tour yet. Everyone just hopes she keeps it up."Jan Willem Luyken, the organiser of Amy's Amsterdam show, confirmed she was alcohol-free.He told Britain's The Sun newspaper: "She wasn't drunk when she came in and she did not drink backstage."I don't think she was stoned either. People were joking about her sober performance. They said, 'Has the wine bar been closed today?' "The 24-year-old star - who is married to Blake Fielder-Civil - has not completely ruled out alcohol on tour and has no plans to stay sober after her performances.During her show in Amsterdam, she told the audience: "Now I want to get drunk again."In August, Amy was forced to postpone her entire North America tour as well as cancel her European dates to allow her time to recover after she overdosed on a mix of heroin, ketamine, cocaine and ecstasy.