Can you identify the author of this quote involving the civil rights movement?

A few years ago (maybe 2½), I remember reading a quote in one of my history textbooks. I believe that it was on the topic of the African-American civil rights movement, and it was probably spoken by a civil rights leader.

Anyways, the quote says something along the lines of “Those who think we have not accomplished anything do not see how far we have come, and those who think that we are finished do not see how far we have to go.”

The main idea is that the civil rights movement is a very long process, and that people often underestimate the amount of societal change that is involved.