Haymitch served as the surly and abrasive yet intelligent mentor to Katniss and Peeta in their Hunger Games. He won the second Quarter Quell when he figured out that the force field could be used as a weapon against the other tributes. After winning the Quell, he became a hostile drunk who isolated himself from the rest of District 12. However, Katniss and Peeta's victory in the Hunger Games seemed to allow Haymitch to open up to others and accept simple acts of kindness.
Though Haymitch has a horrible temper, Katniss admits that he is family now and she could never ask Haymitch to take Peeta's place in the Quell so that Peeta may live. Though Haymitch aggravates Katniss at times, she realizes he is a trustworthy confidant to her and Peeta, especially as she works to protect all of their loved ones. Katniss knows that he is incredibly smart; she values his skills as a mentor. At the end of the novel, Katniss is able to fully understand what Haymitch has known all along: The only way the rebellion will succeed is if she, the mockingjay, comes out of the Quell alive. Haymitch has been working to make a stand against the Capitol, though he has arguably been doing so since he first used the force field to win his Quell years ago. The future of his relationship with Katniss is unclear at the end of the novel as it appears she will never forgive him for leaving Peeta behind or withholding information from them.