Ken is standing on one side of the river and I’m standing on the other. He’s patiently waiting for me to ford the river, too, so we can continue our five-day wilderness hike. It’s early March and the river is swollen with snow melt. Chunks of ice float by in the swift current. To keep my pants and boots dry in the sub-zero weather — an absolute must — I’ve shoved them into the backpack.

I take a deep breath and step into the river.

One foot goes numb. The second foot quickly follows. Shifting the overloaded pack atop my shoulders to center it, I gingerly take another couple of steps in. The water is waist deep and I no longer feel my legs. When I finally climb up the far bank after a couple of near falls, I notice that the snow beneath my feet is pink. I sliced open a foot and didn’t even know it. We bandage the cut and continue on our way.

Ken and I had wanted to do something different for spring break. Falling into the river could have been fatal, but we were college students at the time and full of dreams of adventures — to ford raging rivers, to scale mountains, to trek across deserts or bivouac in the tops of trees. We gave little consideration to planning or training or giving any thought to the consequences if something went wrong.

Reckless moments like these bring to mind advice my father gave me. He was a Naval aviator and he liked to say there are two laws of physics that every pilot knows well. One law is obvious, he’d say. It’s the law of gravity. The other is not so obvious, he’d add. It is the law of averages, which means, if you continue to take unnecessary risks, you eventually crash.

In flight school, he told me they drill the law of averages into cadets. Rash, risky, foolish behavior isn’t tolerated, and shouldn’t be. It not only puts the pilot at risk, it also places his crew-mates, passengers and aircraft in harm’s way. I’ve read that astronauts take the same approach, only more so. Every single move they make has been carefully thought through by teams of experts.

Pilots, Navy Seals, smoke jumpers, commercial fishermen, and … tree workers can’t afford to take unnecessary risks. They never ever should say, “Just go for it.”

Tree workers are not pilots, but we work high enough to cause serious problems if something goes wrong. Our occupation allows little room for error. Like pilots, like astronauts, tree work is not for the timid. Neither is it for adrenaline junkies.

Interestingly, the average age of smoke jumpers is 35. The average age for Navy Seals is 38. The average age for commercial fishermen is also 38. For commercial airline pilots it’s 50. With age comes maturity. With maturity comes the understanding that accidents do happen, particularly when you’re careless.

I’m not sure what the average age is for tree workers. But it is safe to say there are a lot of people well under 35. That’s sobering news for those of us responsible for their training. That lust for adventure, their attitude of being indestructible, their faith that everything will work out, ought to guide us when supervising them.