In The Glass Menagerie, Tom plays the part of the narrator as well as that of the protagonist. Because he is telling us the story of his family, with an emphasis on how it has affected him, a certain degree of detachment on our part is necessary to assess his personality traits.
Tom's main trait is his frustration. This results in anguishing inner struggle, since he feels responsible for his inadequate mother and physically and spiritually crippled sister. He would like to escape the oppressive atmosphere of his home as did his father and take to the sea, but feels torn between his need for freedom and his sense of duty.
Two secondary traits result from the above. He neglects his job and uses his time to write poetry, and gets drunk at bars when he is supposed to have spent the evening at the cinema. The poetry and the drinking are just ways in which he tries to break free from confinement without actually leaving.
Because he finally decides that he must leave, he might be dubbed selfish. It is indeed a complex moral issue whether he should waste his life by sharing the waning fate of his family or whether he is entitled to pursue his own destiny.
At the time he tells the story, he is looking back to the past. An additional trait emerges: Tom has never been able to rid himself of guilt. Although he has succeeded in getting away from the noxious atmosphere of his home, he is not at all sure that he has made the right decision in terms of filial and brotherly duty.