足 stacks a rounded kneecap over 止 (a footprint — the ancient foot picture). Leg from knee down: the foot. How it also came to mean 'enough' is an old borrowing — perhaps a full measure 'stands firm'.
足 kicks and satisfies: 足球 (football/soccer — the nation's beloved heartbreak), 满足 (satisfied — full-enough), 不足 (insufficient). The classical 知足 ('knowing what is enough') is contentment philosophy straight from Laozi: 知足者常乐 — those who know enough are always happy. From World Cup dreams to Daoist calm, 足 covers the distance.
Knee over footprint — the FOOT; a firm stance is ENOUGH.
知足者常乐 'the contented are always happy' — Laozi's happiness formula, hiding inside the word for soccer.