One of the most widespread superstitions is that
every man has his own special, definite qualities; that a
man is kind, cruel, wise, stupid, energetic, apathetic, etc.
Men are not like that . . . Men are like rivers; the water is
the same in each, and alike in all; but every river is narrow
here, is more rapid there, here slower, there broader, now
clear, now cold, now dull, now warm. It is the same with
men. Every man carries in himself the germs of every
human quality and sometimes one manifests itself,
sometimes another, and the man often becomes unlike
himself — while still remaining the same man.

It is not true that men never change; they change for the worse, as well as for the better. It is not true they are ungrateful; more often the benefactor rates his favors higher than their worth; and often too he does not allow for circumstances. If few men have the moral force to resist impulses, most men do carry within themselves the germs of virtues as well as of vices, of heroism as well as of cowardice. Such is human nature — education and circumstances do the rest.

Any man can make mistakes, but only an idiot persists in his error

No-one is equal to anything. Even the same man is not equal to himself on different days.

A man who is used to acting in one way never changes; he must come to ruin when the times, in changing, no longer are in harmony with his ways.

The lesson of forever and ever is that knowing a man's mind ain't knowing the man.

[...] saber si la cuestión de A = A era válido, pues el suponía dos A idénticas, cuando sólo podía haber una A idéntica a sí misma y, sea como fuere, referido a la realidad aquello era un absurdo, ningún hombre era idéntico a sí mismo porque estaba sometido al tiempo y, en rigor, en cada momento era distinto del que había sido en el momento anterior, a veces él tenía la impresión de ser otro cada mañana, como si un nuevo Yo hubiera desplazado a su Yo anterior y utilizara ahora su cerebro y, por lo tanto, también su memoria [...]

One of the commonest and most generally accepted delusions is that every man can be qualified in some particular way — said to be kind, wicked, stupid, energetic, apathetic, and so on. People are not like that. We may say of a man that he is more often kind than cruel, more often wise than stupid, more often energetic than apathetic or vice versa; but it could never be true to say of one man that he is kind or wise, and of another that he is wicked or stupid. Yet we are always classifying mankind in this way. And it is wrong. Human beings are like rivers; the water is one and the same in all of them but every river is narrow in some places, flows swifter in others; here it is broad, there still, or clear, or cold, or muddy or warm. It is the same with men. Every man bears within him the germs of every human quality, and now manifests one, now another, and frequently is quite unlike himself, while still remaining the same man.

Man is never perfect, nor contended.

All the basic situations in life occur only once, never to return. For a man to be a man, he must be fully aware of this never-to-return. Drink it to the dregs. No cheating allowed. No making believe it's not there. Modern man cheats. He tries to get around all the milestones on the road from birth to death.

Remember that every man is a variation of yourself

All man are the same except for their belief in their own selves, regardless of what others may think of them

...each living creature is said to be alive and to be the same individual — as for example someone is said to be the same person from when he is a child until he comes to be an old man. And yet, if he's called the same, that's despite the fact that he's never made up from the same things, but is always being renewed, and losing what he had before, whether it's hair, or flesh, or bones, or blood, in fact the whole body. And don't suppose that this is just true in the case of the body; in the case of the soul, too, its traits, habits, opinions, desires, pleasures, pains, fears — none of these things is ever the same in any individual, but some are coming into existence, others passing away.

At bottom every man knows well enough that he is a unique being, only once on this earth; and by no extraordinary chance will such a marvelously picturesque piece of diversity in unity as he is, ever be put together a second time.