The key is to keep company only with people who uplift you, whose presence calls forth your best. Epictetus
Marriage is the key of moderation, the harmony of desires, the seal of a deep friendship ... the unique drink from a fountain enclosed, inaccessible to those without. United in the flesh, one in spirit, they urge each other on by their mutual love. Gregory of Nazianzus
The key to growth is the introduction of higher dimensions of consciousness into our awareness. Laozi
Doubt is the key to knowledge. Persian Proverb
Keep learning because knowledge is the key to power. Polish Proverb
"if I rest, I rust,” says the key. German Proverb