On your first appearance before the Court, do not waste your time and ours telling us so. We are likely to discover for ourselves that you are a novice but will think none the less of you for it. Every famous lawyer had his first day at our bar, and perhaps a sad one [….] Be respectful, of course, but also be self-respectful, and neither disparage yourself nor flatter the Justices. We think well enough of ourselves already.

Robert H. Jackson (1892-1954) US Supreme Court Justice (1941-54), lawyer, jurist, politician

“Advocacy Before the Supreme Court,” Morrison Lecture, California State Bar (23 Aug 1951)
    (Source)

Reprinted in the Cornell Law Quarterly (Fall 1951). Legal citation "Advocacy Before the Supreme Court," 37 A.B.A.J. 801, 803 (1951).