People who are upset about something ruminate on it whenever they get a chance; they are constantly drawn back to their own unhappy tale as if it were a horror story left open on a table.

Nothing is more dangerous than an idea when it is the only one you have.

Profound sadness is always the result of an unhealthy condition of the body. ... We [should] say, 'I am sad; everything looks black to me; but external events are in no way responsible. It's my body that insists on reasoning. These are the opinions of my stomach.'

One must be truthful with oneself about one's own motives, especially if one is to survive in the world. It takes rigor, and it takes courage.

It is not difficult to be unhappy or discontented; all you have to do is sit down, like a prince waiting to be amused. ... It is impossible to be happy if one does not have the desire to be happy; one must therefore will one's happiness, and create it.

We must recognize the eloquence of our passions and refuse to be taken in. Instead of saying, 'That false friend always did despise me,' say: 'In my present state of agitation, I can't see clearly, I can't judge clearly; I am only a tragic actor who is declaiming for his own ears.' Then you will see the lights in the theater go out for lack of an audience, and the brilliant sets will be nothing more than painted cardboard.

To think is to say 'no.'