Oscar Wilde: Thing

Variant: One of the great secrets of life. Most people die of a sort of creeping common sense and discover too late that the only things one never regrets are one's mistakes.
Source: The Picture of Dorian Gray

Source: The Picture of Dorian Gray

Lord Goring, Act I
Variant: The only thing to do with good advice is to pass it on. It is never of any use to oneself.
Source: An Ideal Husband (1895)

Source: The Picture of Dorian Gray

Source: The Picture of Dorian Gray

The Soul of Man Under Socialism (1891)
Context: The only thing that one really knows about human nature is that it changes. Change is the one quality we can predicate of it. The systems that fail are those that rely on the permanency of human nature, and not on its growth and development. The error of Louis XIV was that he thought human nature would always be the same. The result of his error was the French Revolution. It was an admirable result. All the results of the mistakes of governments are quite admirable.

Review of Herbert Giles translation of the works of Zhuangzi (Chuang Tsu) in The Speaker (8 February 1890)

The Soul of Man Under Socialism (1891)
Context: Art is the most intense mode of individualism that the world has known. I am inclined to say that it is the only real mode of individualism that the world has known. Crime, which, under certain conditions, may seem to have created individualism, must take cognisance of other people and interfere with them. It belongs to the sphere of action. But alone, without any reference to his neighbours, without any interference, the artist can fashion a beautiful thing; and if he does not do it solely for his own pleasure, he is not an artist at all.

Said about Absinthe https://en.wikipedia.org/wiki/Absinthe. Quoted in “Letters to the Sphinx from Oscar Wilde: With Reminiscences of the Author" by Ada Leverson (London: Duckworth, 1930)

Lord Goring, Act I
An Ideal Husband (1895)

Source: The Importance of Being Earnest

Source: The Picture of Dorian Gray