The change in the narrator's attitude in Norman Levine's "We All Begin in a Little Magazine" is, indeed, inevitable. We see in the main character a man who had to make a choice: either he will go along continuing to live the bohemian lifestyle of a writer, or he will snap out of it, grow up, mature, and engage in that lifestyle only as much as his economic means allow him to.
The second attitude makes much more sense to a man who wishes to have a family and lead a "normal life". However, the narrator's words make us wonder if that is what he really wanted to do with his life, deep inside. Was he a man made out to have a normal life? Or was his "normal" the bohemian life that survives by the skin of its teeth?
The encounters with the different hopeful writers that visited the doctor's house bring back the memories of the man that he once was; it was a time that he describes as "one of his happiest times" despite of all the bad things that, as he describes, were going on around him: the "seediness of the people's clothes", being "broke", only having "enough money for a hamburger, coffee and a small cigar", the many things he had to do.
This is why, in the end, he felt the need to leave. Just like he had to leave the lifestyle that best fit him as a result of the mundane economy, he also had to leave his true heart and feelings behind. He would go back to the life that he chose to live, albeit begrudgingly. This is the reason for the ending to be the way that it is. Whe he hears a female writer asking for the doctor, and she asks him whether he (the narrator) had read her manuscript, he answers in the negative. When the girl on the phone asks the poignant question: "Are you not one of us?", the last word he utters is a very painful: "No".