Sailing is easy. Big boats, say of around fifty feet, can easily be sailed by one or two competent sailors.
If making long passages across seas or oceans of more than a few days, unless you're young and fit,
its the watch keeping around the clock that wears you down quickly through sleep deprivation / interruption.
This is assuming you have the sails well trimmed, boat nicely balanced and the autopilot switched on as a fall back,
so the boat basically sails itself with no/minor inputs.
Despite radar and ship proximity alarms on ocean going yachts and commercial traffic. Merchant ships don't always maintain a bridge watch. Unless
you maintain a watch, you could easily be run down, especially at night and no one might ever know what happened to you. If solo and far from land, you really ought to be up every couple of hours
to check the boat, systems and sea around you. If short handed, watches of six hours on and six hours off may suit the crew. The more competent crew you have, who know when and when not to wake up the captain, the happier the captain is
When I was half my current age, work responsibilities demanded that I sometimes went without sleep for thirty-six hours or more, but I was a zombie at the end of it and close to ineffective.
Being up every two hours and possibly preventing myself from getting into deep sleep, gets hard after a week or so. A fortnight is really pushing it and is not enjoyable.