CHICAGO — She looked around and saw herself three decades ago, young and uncertain, from a part of town where success is a struggle, not a birthright. She knew what they had been through, what it was like to take the long way home to avoid gangs, what it was like when the family strained to make ends meet.

For Michelle Obama on Tuesday night, addressing a graduating high school class from the South Side near where she grew up summoned memories and offered a chance to draw lessons from her own upbringing: Never be afraid to ask for help, she told them. Instead of being discouraged by hardship, reach higher.

At a time of roiling debate over the issues of race and opportunity, punctuated by the events of Ferguson, Mo.; Staten Island; and Baltimore, the nation’s first African-American first lady has added her voice. It is not a new message for her, but one that has taken on special resonance and one delivered with bracing candor in recent speeches. Along the way, Mrs. Obama has opened a window into her own life, not just in Chicago but also in the White House.

By her telling, even living at the world’s most prominent address has not erased the sting of racial misunderstanding. In recent weeks, Mrs. Obama has talked of “insults and slights” directed at her husband and caricatures that have pained her. It all “used to really get to me,” she said, adding that she “had a lot of sleepless nights” until learning to ignore it. But she said she realized that she and her husband had a responsibility to rewrite the narrative for African-Americans.