Sober

Definitions: (1) showing self-control; not extreme in any way; practicing a reasonable and moderate use of substance or emotion; temperate; (2) regularly displaying calm reason; cool; (3) having a serious, earnest, or thoughtful nature; solemn; (4) quiet; not flashy; (5) honest; not exaggerated <the sober truth>; (6) sane; rational

Balancing Qualities: Enthusiastic, Spontaneous

Quotes:
True heroism is remarkably sober, very undramatic. It is not the urge to surpass all others at whatever cost, but the urge to serve others at whatever cost. — Arthur Robert Ashe Jr. (1943-1993) American tennis player
• Elegance is achieved when all that is superfluous has been discarded and the human being discovers simplicity and concentration: the simpler and more sober the posture, the more beautiful it will be. — Paulo Coelho de Souza (1947-) Brazilian lyricist & novelist