"Passport Envy" is a stage theorized by Sigmund Freud regarding travel development, in which holders of one passport experience anxiety upon realization that they do not have two of them. Freud considered this realization a defining moment in a series of transitions toward a mature travel experience and traveler identity. In Freudian theory, the passport envy stage begins the transition from an attachment to the suitcase to competition with the neck pillow for the attention, recognition and affection of the amenities kit.