In the beginning of the book Sydney Carton is a selfish and depressed alcoholic. He thinks his life is useless and doesn't care about himself. A quote that shows this is "bring me another pint of this same wine, drawer, and come and wake me at ten."
Sydney then falls in love with Lucie Manette. Lucie doesn't feel the same way. Sydney accepts the facts that she doesn't love him because he just wants her to be happy. A quote that shows this is "For you, and for any dear to you, i would do anything."
Lucie ends up getting married to Charles Darnay. Sydney respects it and doesn't get mad or sad because he just wants here to be happy. A quote that shows this is "I know that when she is clinging t you, the hands of baby, girl, woman, all in one, are round your neck."
Charles Darnay is going to be killed but Sydney Carton decides sacrifice himself to save Charles. He does this because he thinks he's had a bad life and wants to make up for it. A sentence that shows this is "I see him winning it so well, that my name is made illustrious there by the light of his..."