Choosing the right size carrier for your cat is crucial because a carrier that's too large can cause your cat to tumble around during transport, leading to stress or injury. Conversely, a carrier that's too small can make your cat feel trapped and frightened, increasing anxiety. The ideal carrier size allows your cat to sit up, turn around, and lie down comfortably, ensuring safety and security. This balance helps maintain your cat's comfort and reduces stress during trips, making the experience more positive for both of you.