A mature person is one who does not think only in absolutes, who is able to be objective even when deeply stirred emotionally, who has learned that there is both good and bad in all people and all things, and who walks humbly and deals charitably with the circumstances of life.

The quotation defines “maturity” less as age than as a disciplined moral and intellectual posture. It emphasizes resisting black‑and‑white thinking, maintaining objectivity amid strong feeling, and recognizing moral complexity in oneself and others. The closing clauses—walking humbly and dealing charitably—shift from cognition to character: maturity is shown in how one treats people and meets life’s contingencies, not merely in private judgment. Read this way, the line aligns with a civic-minded ethic often associated with Roosevelt: emotional self-command, tolerance for ambiguity, and compassion as practical virtues in public and personal life.