A man who had enjoyed a pleasant day said he suddenly snapped and became angry.
Stuart Bailey said he decided to go for a walk, but he took a knife and started headbutting a metal gate.
Bailey, 36, of Chatsworth Road, Fleetwood, pleaded guilty to possessing a blade in public.
He was bailed for sentence by District Judge Jeff Brailsford sitting at Blackpool Magistrates’ Court.
Jim Mowbray, prosecuting, said police had a tip-off on September 8 and went to the port’s Princess Way where Bailey told officers he had a knife in his pocket.
Bailey said he had drunk four lagers, a bottle of wine and some vodka, but he was not drunk. He added he was on medication for anxiety.
Brett Chappell, defending, said: “He seemingly out of nowhere just snapped. Nothing took place to warrant his behaviour.”