At the game, Lester first sees Angela. Immediately, Lester begins to fantasize about Angela. He pictures Angela on the gym floor all alone, dancing just for Lester, as if they were the only two people in the room. Lester is in awe at how beautiful he feels Angela is. After the game, Jane introduces Lester and Angela, at which point Lester has trouble coming up with something to say and he stares directly at Angela. The scene resembles a teenage boy looking at a beautiful woman, not a grown, married man looking at a teenage girl. Angela can see from this that Lester is in awe of her beauty and she is flattered by it.
Angela presumes that every man that she meets will fall in love with her beauty. When Lester stares directly at her, she is not surprised. Later in the movie, when discussing the incident with Jane, Angela states "I think he's cute." She is referring to Lester and Jane feels very uncomfortable about the whole situation. This adds to tension that has already become between Jane and her parents. Angela goes along with Lester's fantasy and creates tension between her and Jane. The addition of Angela to Lester's life ends up bringing out much friction in the Burnham household that has been kept quite up until this point. Angela promotes Lester's fantasy about her, which drives Lester farther from his wife.
By Angela's actions and Lester's distance from his wife, Lester actually becomes more in touch with reality. He realizes that he no longer enjoys his job, and that he is unhappy with the way he is leading his life. Lester quits his job and takes a new job at a fast-food restaurant. After realizing that he was not happy with his life, Lester continues to make dramatic changes to his life. When he first meets Ricky next door, he starts smoking marijuana again for the first time in many years. He then trades in his car on an old Pontiac Trans Am that he had always wished to have.