In 1620, the people we call the Pilgrims did something incredibly foolish. They packed themselves into a dank, overcrowded space on a ship called Mayflower and set sail for a distant world. As happens in any untried venture, they made many mistakes. But they got the fundamentals right, and with a dollop of luck — or call it divine providence — they accomplished the impossible.

Their mistakes would seem to doom the venture. They leased the Mayflower — smart move — but they also bought a ship called the Speedwell. But the only thing the Speedwell did well was leak. After two midsummer attempts to sail west, they gave up on the Speedwell. They packed 102 men, women, and children into the Mayflower, and on September 16 shoved off for good.

Big mistake. It would take two months to reach the New World. It would be snowing by the time they arrived, way too late to plant crops and a difficult time to build houses. What were they thinking?

They weren’t thinking about hurricane season, which is what they were sailing into. They hit a few storms, one of which was no place for a wooden ship. A wave hit them broadside so hard it cracked a stout oak beam. One more hit and the ship would crack in half. But by luck, working in pitch dark in a lurching ship, they found a house jack and forced the beam back into position.

They were aiming for someplace just south of the Hudson but arrived just north of Cape Cod — not bad for a navigator working with just a couple of sticks, a long piece of string, and a sliver of magnetized iron. For reasons unknown, they decided to settle there instead of down south. Maybe they expected weather like that of balmy Barcelona, which was just as far north.

If so, they were wrong. Snow was falling, the ground frozen. They had to spend the winter aboard the ship. Packed hip-to-hip in the windowless deck, they infected each other with a respiratory disease. By February, almost half had died.

They ran out of beer. Food ran short. Then they discovered that someone had forgotten to pack the fishhooks. Hunting was tough because their firearms depended on smoldering hemp. Wandering the woods in a cloud of cannabis smoke, they had trouble finding game.

And then, in March, suddenly, just outside the settlement, local people started shouting and brandishing bows and arrows. The settlers had to make a big decision — to fire off a preemptive volley to scare off the “savages,” or, in Christian and political wisdom, offer goodwill. If they made the wrong decision, they’d be dead Pilgrims.

A few men went outside the palisade and laid their weapons on the ground. There they stood, as brave as men but vulnerable as babes. The locals understood the gesture. They approached unarmed. The mutual goodwill allowed the Pokanoket and the English to become good friends.

And then — talk about luck! — along came a local who spoke fluent English, the man we know as Squanto. Squanto had already been across the Atlantic four times. Arriving the last time, he found his entire tribe, the Patuxet, dead of disease. Everyone figured the land was cursed. Nobody wanted it. If the English chose to settle there, nobody cared.

Bad mistakes resulted in the deaths of half the Pilgrims. Dumb luck helped the rest survive. But it was fundamental values that allowed Plymouth to thrive. The Pilgrims had come as families. They had come to work and build new lives, not get rich quick off gold, slaves, or conquest. They took their Christianity seriously, achieving peace through goodwill. They stuck together. They promoted the general welfare. They planted the seeds that grew into a nation. This is what we remember on Thanksgiving. For this we still give thanks.

Glenn Alan Cheney is the author of 'Thanksgiving: The Pilgrims’ First Year in America.' He lives in Hanover.