Why does Freak lie to Max?

Freak's relationship to Max is characterized by deception. He is not honest with Max about his illness, absences from school, or his terminal diagnosis. Understandably he desires to spare his friend the pain of knowing the temporary nature of their relationship, so his intentions are loving, but Freak is still not telling Max the truth. He actually robs his friend of valuable time and emotional space to prepare for Freak's death. Although Max is not forthcoming about his parents, he keeps this information to himself out of embarrassment. The subject is really painful for Max. While Freak must also suffer from the weight of the knowledge of his death, he is not embarrassed by the illness. He deliberately chooses not to tell Max about his diagnosis because he doesn't want to burden his friend, but this decision in and of itself demonstrates Freak's inability to process his own impending death.