Tommy Wilhelm, the protagonist of Seize the Day, is a character in turmoil. He is burdened by the loss of his job, financial instability, the separation of his wife, and his relationship with his father, among other things. He is a man in search of self who the reader is allowed to watch and follow through the course of a single, significant day in his life, a day that is called his "day of reckoning."

Tommy is a complicated and layered character who wears masks and has to peal away his social armor and mask in order to understand himself, at the end of the book. The book begins, "when it came to concealing his troubles, Tommy Wilhelm was not less capable than the next fellow. So at least he thought…" Concealment is an issue at hand. Significantly, Tommy had been an actor, albeit a failed one, as well as a salesman. He had learned to wear masks, play roles, and "sell" himself. However, on the day that the narrative takes place, Tommy must rid himself of all of this and find out who he really is.

Tommy, it is evident, plays many roles. He plays the role of Adler's son, a role that is difficult for him to escape. He cares too much how his father sees him. And, he often becomes the "failure" that he believes his father sees in him. He has been an actor, a hospital orderly, a ditch-digger, a seller of toys, a seller of self, and a public relations man for a hotel in Cuba. He has, therefore, been many characters and never his true self. Beneath his masks, as the reader is privileged to discover through interior monologues, he is truly an introvert trapped in the body of a man who has been forced to be extroverted, he is also sensitive and almost, at times feminine. This femininity is poked at and criticized, however, by his father when he accuses him of having had a relationship with a man from his office.

The novel portrays Tommy as a man who is drowning. The imagery that surrounds him is the imagery of water and he is constantly "descending" and "sinking" into hellish depths. However, the author must bring into question the character of Tommy because although he constantly blames others, such as his father, his wife, or Dr. Tamkin, for his strife and place in life. He must learn to take credit for his own mistakes. He is character in flux, a character that wavers between victimization and a temptation to martyrdom and a self-acceptance, and he wavers too between childishness and maturity. Nevertheless, it is this very fluctuation that will help him on his way to seeking truth because, as Dr. Tamkin says, the path to victory is not a straight line.