There is no knowledge so hard ...

There is no knowledge so hard to acquire as the knowledge of how to live this life well and naturally.
There is no knowledge so hard to acquire as the knowledge of how to live this life well and naturally.

Quotes from the same author

I care not so much what I am to others as what I am to myself. I will be rich by myself, and not by borrowing.
If there is such a thing as a good marriage, it is because it resembles friendship rather than love.
The most certain sign of wisdom is cheerfulness.
The most unhappy and frail creatures are men and yet they are the proudest.
It is much more easy to accuse the one sex than to excuse the other.