In The Glass Menagerie,
Tom lives with his mother and disabled sister and works at a job that he hates to help support them. But he spends most of his home life arguing with his mother and goes to the movies every night to get away from his family.
That sounds a bit selfish, doesn't it?
But in reality, Tom's mother is the cause for most of their arguments because she dismisses the things that are so important to him. Tom enjoys poetry and has dreams of living an adventurous life and seeing the world — all of which are qualities Tom inherited from his father, who walked out on the family. Tom's mother vilifies her estranged husband and his wanderlust, and therefore sees these traits in Tom as the root of his discontent. Tom's mother even confiscates some of the books that Tom buys with his own money in an attempt to get him to settle into what she considers a more "normal" life.
At the end of the play, Tom's mother again reminds him that he is a selfish dreamer who never thinks about his "mother deserted and an unmarried sister who's crippled and has no job." Having had enough, Tom does finally walk out on them, but then tells the audience that he could never forget his sister. Wherever he goes, he still thinks about her.
This makes it clear that Tom's leaving wasn't a selfish act. He didn't want to live his life working in a shoe factory, watching his intellect and his dreams and his creativity slowly draining away. Tom recognized that he had to leave to save himself. It was an act of self-preservation. He knew that if he stayed, he would be destroyed as an artist. But as an artist, and as a sensitive man, he has never been able to forget his life — and especially the delicate charm and loveliness of his sister.