Option 1 -> "produce life" doesn't make logical sense in this context.
Option 2 -> "curtail" means to reduce or shorten; mental fatigue shortening life explains why structured living is important.
Option 3 -> "prolong" means to extend life, which would contradict the reason for needing a structured lifestyle.
Option 4 -> "procure" means to obtain or acquire, which doesn't fit the context of life's duration.
Hence, Option 2: curtail -> The sentence emphasizes the importance of a structured life by highlighting that mental fatigue can actually shorten or reduce lifespan, providing a compelling reason for maintaining structure and avoiding mental exhaustion -> correct