The world is afflicted by death and decay. But the wise do not grieve, having realized the nature of the world.

Buddha

You study, you learn, but you guard the original naivete.

Henri Matisse

In solitude the mind gains strength and learns to lean upon itself.

Laurence Sterne

Don't be distracted by emotions like anger, envy, resentment. These just zap energy and waste time.

Ruth Bader Ginsburg

Knowing yourself is the beginning of all wisdom.

Aristotle

Wisdom is knowing what to do next, skill is knowing how to do it, and virtue is doing it.

David Star Jordan