Sailing is easy. Cloth sails are trimmed to harness the energy of the wind to move the boat forward. The hull shape prevents the boat from being simply pushed downwind. With experience, a number of fine adjustments make sailing more efficient, with only two lines, you can effectively sail a boat.
Sure, you have to deal with the weather, obstacles, currents, and tides, but most of those elements come at you in slow motion. There is time to think through them and come up with a solution. In fact, nearly every issue on a boat can be dealt with in slow motion, except for fire or man overboard.
Maneuvering into a berth is a bit different. Sure, it’s done slowly, but you’re quite literally wedging your boat between a “dock and a hard place.” Some may think it’s similar to parallel parking a car, and there is some similarity, in that reverse is used. After that, it’s a totally unique experience. Picture your car having balls instead of wheels, meaning it can move back and forth, but also sideways and crossways, and zigways and zagways. Now picture those balls are made of polished steel and the road is covered in ice. Stopping is no longer an act of tapping the brake… no, stopping is a combination of turning the wheel and applying the throttle to the precise position.
Now comes the interesting part… imagine that the road isn’t stable, it sways and flows under you with currents and tides that you can’t see from the surface. It also ungulates from waves and wakes thrown off by other boats in the marina. And just for good measure, add the wind, which pushes you around in ways that are mostly uncooperative. Jamming your bow into your neighbor or worse, crashing into the pier.
Like I said, sailing is easy. Maneuvering, on the other hand, is where ulcers begin.