No one can make you feel inferior without your consent.

Eleanor Roosevelt (1884-1962) First Lady of the US (1933-45), politician, diplomat, activist

(Attributed)

Sometimes cited to her autobiography This is My Story (1937), but not found in that book. It seems to have been inspired by a comment she made in 1935: "A snub is the effort of a person who feels superior to make someone else feel inferior. To do so, he has to find someone who can be made to feel inferior."The quotation was in its present form (and attributed to her) by 1940. More information here.