Throughout history, people have used mechanical devices as a metaphor for the human body.
The lungs evoke mechanical pumps, which the Greek physician Galen picked up on when he suggested that they take in pneuma, the vital life force, and distribute it throughout the body.
Your "biological clock" suggests something unwavering, ticking away inside of you. But a single bright light can throw off your circadian rhythm. And if you fly to a different time zone, your body can take days to catch up, unlike a regular clock, which can simply be reset.
More recently, computers have served as a metaphor for the brain. Computers cannot create consciousness, though. They never get tired and aren't capable of empathy.
These models serve as a way of simplifying the biological processes happening inside us. But if you're doing a job that a computer or robot cannot, then you are more than the sum of your mechanical parts.
We do our best work when we approach it with this holistic appreciation for ourselves. Some days are more or less productive than others, because you are an organic being. Full of life and emotion and intelligence and compassion.
How glorious is that?