I am installing the headlight on my new bike and as the manual says I out three washers on the bolt, put the bolt through the fender mount, then through the head light, then trough the fork, then one more washer and the nut on the end. but I have tightened it to the point that the nut started to slip in the wrench but the headlight will still slight all over the place with almost no effort.

anyone have any tips on how I can fix this?