The Arctic tern flies from pole to pole and back again each year — roughly 44,000 miles. Over its lifetime, it covers a distance equivalent to three round trips to the moon. It weighs less than a coffee cup. There is no reasonable explanation for why this should work, and yet it does, every year, without fail.
Migration is not a journey but a commitment written into the blood. Bar-tailed godwits cross the Pacific in a single nine-day flight, sleeping with half their brain at a time, burning their own organs for fuel. They arrive in New Zealand lighter by half and begin eating immediately.
I think about the godwits when I am tired and consider giving up on something difficult. They do not consider. They simply fly.