Final answer:
Chief Joseph is conveying deep exhaustion and sadness over the suffering and losses of his people, culminating in his decision to cease fighting.
Step-by-step explanation:
The speaker, Chief Joseph, in the passage is expressing a profound sense of exhaustion and despair over the ongoing struggles and losses his people have faced. The heart-wrenching details of the Niimíipuu (Nez Perce) suffering, including the death of tribal chiefs and the desperate circumstances of his people without food or shelter in the cold, lead to his ultimate decision that he can no longer continue to fight. Chief Joseph's speech is a poignant surrender, expressing that his heart is sick and sad, and making it clear that from that moment he will fight no more forever.