Justice John Marshall Harlan I (the namesake of the Harlan Institute) on being in the dissent:

“Of course I am wrong, because only the Chief Justice, and myself held those views, and as the majority decided the other way, we must believe that we were wrong.”

Justice John Paul Stevens on Bush v. Gore, in which he dissented:

” I don’t question the good faith of the people, the justices with whom I disagreed. But I think they were profoundly wrong.”

Stevens also joked about the mistakes of the Court.

“Where does the court make a mistake, in your view?” Pelley asked.

“Well which mistake do I want to emphasize?” Stevens asked.

See also Justice Sotomayor’s comments about being in the dissent, for more context for the Justice Harlan quote.