A fellow goes to the train station and wants to buy a ticket to pittsburg but upon looking over the counter he sees a beautiful girl with huge tits and instead he says "I'd like a ticket to TITSberg". Upon saying this he becomes embarrassed and goes red.
A fellow standing along side starts to console him. 
He says "Its all right - I'm a psychologist and what has happened here is perfectly natural - Its what they call a Freudian slip - Freud postulates that we think about sex a thousand times a day and when we see it in front of us, sometimes we make these small slips of the tongue - here - I will give you an example - The other day I was sitting on my porch having breakfast with my wife and I meant to say to her 'Excuse me dear, can you pass the sugar over here please' but when I looked at my wife I opened my mouth and said 'You fat ugly slut, you've ruined my f**king life'".