When your opponent sees into your reasoning like a lynx, conceal your thoughts like an inky squid. - Baltasar Gracián

Don't so belong to others that you don't belong to yourself. Even friends should not be abused; you shouldn't want more from them than they're willing to concede. Any extreme is a vice, and especially in dealings with others. Sensible moderation is the best way to maintain goodwill and respect because ever-precious dignity won't be worn away.

La virtud es cosa de veras, todo lo demás de burlas. La capacidad y grandeza se ha de medir por la virtud, no por la fortuna. Ella sola se basta a sí misma. Vivo el hombre, le haze amable; y muerto, memorable.

A man should not employ all his capacity and power at once and on every occasion. Even in knowledge there should be a rearguard, so that your resources are doubled. One must always have something to resort to when there is fear of a defeat. The reserve is of more importance than the attacking force: for it is distinguished for valour and reputation.