Failure to read what is happening in another's soul is not easily seen as a cause of unhappiness: but those who fail to attend the motions of their own soul are necessarily unhappy.

A man should always have these two rules in readiness. First, to do only what the reason of your ruling and legislating faculties suggest for the service of man. Second, to change your opinion whenever anyone at hand sets you right and unsettles you in an opinion, but this change of opinion should come only because you are persuaded that something is just or to the public advantage, not because it appears pleasant or increases your reputation.

If this is neither my own badness, nor an effect of my own badness, and the common weal is not injured, why am I troubled about it? And what is the harm to the common weal?

And can anything else that is useful be accomplished without change? Do you not see then that for yourself also to change is just the same, and equally necessary for the universal nature?

Never let the future disturb you. You will meet it, if you have to, with the same weapons of reason which today arm you against the present.

The greatest part of what we say and do is really unnecessary. If a man takes this to heart, he will have more leisure and less uneasiness.

The world is mere change, and this life, opinion.