First, it's important to determine the character of the young man before we begin our letter. Identifying the young man's temperament and personality-type will help us to stay as true to character as possible. This will lend an authentic quality to the letter we write. From the story, we can see the young man considers himself cosmopolitan and wise. Nonetheless, he prizes purity above all else in a woman.
The story begins with the young man going on vacation with his girlfriend. She's twenty-two, and he's twenty-eight. One quality the young man likes about his girlfriend is her innocence; she's unlike all the other girls he has dated. Let's take a look at some quotes that can help formulate a letter:
He enjoyed her moments of shyness, partly because they distinguished her from the women he'd met before, partly because he was aware of the law of universal transience, which made even his girl's shyness a precious thing to him.
Now sitting face to face with her, he realized that it wasn't just the words which were turning her into a stranger, but that her whole persona had changed, the movements of her body and her facial expression, and that she unpalatably and faithfully resembled that type of woman whom he knew so well and for whom he felt some aversion.
He had the paradoxical honor of being himself the pretext of her unfaithfulness. This was all the worse because he worshiped rather than loved her. It had always seemed to him that her inward nature was real only within the bounds of fidelity and purity, and that beyond these bounds it simply didn't exist. Beyond these bounds she would cease to be herself, as water ceases to be water beyond the boiling point.
. . . everything was in the girl, that her soul was terrifyingly amorphous, that it held faithfulness and unfaithfulness, treachery and innocence, flirtatiousness and chastity. This disorderly jumble seemed disgusting to him, like the variety to be found in a pile of garbage.
The first quote illustrates how the young man views his girlfriend; he worships her as if she is purity personified. The second quote marks a transition, a change in the way he now sees her: she has become a stranger acting out the part of a seductive woman, and he's not sure he likes what he sees. The third quote highlights his dawning disillusionment and encroaching doubts about her true character. The fourth quote illustrates his outright hatred of her.
Subsequently, the young man proceeds to humiliate his girlfriend, exhibiting the kind of callous behavior he only reserves for prostitutes and women he respects very little. The story ends with the young man in the uncomfortable role of comforter; once the game comes to a shattering end, he must come to terms with his own jealousies and inadequacies as well as work to restore the relationship to its former familiar terrain.
Based on the above, we can accompany a narration of the trip with the young man's evolving impression of his girlfriend. This is one way we can make the letter authentic. Below, I include a guide on how to proceed:
1) As the young man, begin the letter describing where you're headed with your girlfriend. You have a stressful job; there's nothing in life you appreciate more than "lightheartedness." Luckily, your girlfriend has that quality in spades, and you're looking forward to enjoying some time with her.
2) Describe your girlfriend and what you like about her, especially her shyness (which you think is endearing). You like to tease her and watch her reactions when you do. Illustrate what you mean by her shy ways: describe what happens when you stop at a gas-station and she asks to "take a little walk."
3) Despite all these good traits, there is one trait your girlfriend exhibits which worries you a little bit. She seems to envy the flirtatious girls you've dated before her. You try to reassure her that you only have eyes for her, but she doesn't believe you. Including this tidbit of information is important, because it will allow you to transition into the "game."
3) The "game" begins. Describe how you are now a stranger and your girlfriend is the hitchhiker. You exchange banter (refer to the story to include any details you deem pertinent to your letter). Eventually, you make a comment which irritates your "hitchhiker." This makes you want to stop the "game."
4) Your girlfriend doesn't want to stop playing the game. She wants to pretend to be the kind of woman she thinks you like. By now, you're irritated. Describe how you decide to display your frustration: "he stopped making the gallant remarks with which he had wanted to flatter his girl in a roundabout way, and began to play the tough guy who treats women to the coarser aspects of his masculinity: willfulness, sarcasm, self-assurance."
5) You decide to teach your girlfriend a lesson. Instead of heading for your initial destination, you tell her roughly that you will take her somewhere else. Describe the exchange you have with her and why it bothers you. Remember to write as if you are explaining your feelings to someone else.
6) You arrive at a hotel at Nove Zamky, and you don't like what you see (describe why). In truth, you're not really the callous persona you pretend to be, and you feel uncomfortable acting this way. Explain why you feel the need to keep up the pretense.
7) During a conversation at dinner, you realize you are beginning to feel uncomfortable with the way your girlfriend is acting. Explain why (again, please refer to the text for details).
8) Your girlfriend goes to the bathroom. On the way back, she flirts with a strange man. Describe your emotions and what you decide to do as a result: you take her back to the hotel room and proceed to treat her as if she is a prostitute you hired for the night. Again, please refer to the text to help you with the details.
9) Last, describe what happens after you have sex with your girlfriend. The spell is broken, and you are both horrified at how you've acted. Explain your emotions when you realize that you still have thirteen days left to vacation with your girlfriend.