How does trying to keep his promise affect Sam McGee's friend?

In Robert W. Service's poem "The Cremation of Sam McGee," Sam McGee's friend is deeply affected by his promise to cremate Sam after his death in the harsh Yukon wilderness. This obligation drives the friend to undertake a challenging and emotionally taxing journey, ultimately leading him to confront the stark realities of loss and isolation. The friend's determination to honor Sam's wish highlights themes of loyalty and the burdens of promises, illustrating how such commitments can profoundly impact one's mental and emotional state.