Good sense is the most equitably distributed thing in the world,
判断力是世界上最公平的东西
for each man considers himself so well with it that even those who are most difficult to satisfy in everthing else do not usually wish to have more of it than they have already.
有的人自觉判断力很强,对其他事物也许觉得难以满足,但也绝不会再希求更多的判断力.
意思是说：人们对判断力的需求是平衡的,如果有的人觉得足够了,就不会再想要了
我觉得可能是因为过多的判断力可能对人造成伤害,可能是“难得糊涂”的意思.