as a boy i read many books about the great big sailships crossing the oceans .
at that time there were still sailships bringing bringing "guano" (bird droppings) from chile to europe .
one of the rules the sailors lived by , was "One Hand for Yourself - One for the Ship " .
i've always interpreted that more broadly : if you are doing anything or helping someone , never forget that you have to make sure that you don't forget yourself completely . if you give both hands to the ship , you might very well be lost overboard - and you won't be any good to your shipmates or yourself .