Here's why:
* The Games are a Cruel Show: The Hunger Games are designed by the Capitol to entertain and control the districts. The Capitol doesn't care about the tributes' lives; it cares about the spectacle.
* Survival is the Goal: Haymitch, a former victor, knows the Games are brutal and that survival is the ultimate goal. He tells Katniss to focus on that.
* The Allies are False: Katniss, having lost her family to the Capitol's policies, sees the other tributes as potential threats. They are all pawns in the Capitol's game.
* The Capitol Controls Everything: The Capitol manipulates the Games, the tributes, and the Districts. Their goal is to maintain power and control. Katniss understands that the Capitol is the enemy and that the Games are just another tool in their arsenal.
Haymitch's advice is a reminder that Katniss needs to stay focused on her goal of survival and to prioritize her own safety above all else. He is warning her not to trust anyone in the arena, even those who seem friendly. The true enemy is the Capitol, and Katniss needs to fight for her own survival against it.